AHE-250-D02 Service Manual

System Specifications

Electric Element

Power Consumption ......................................1000 W (maximum)

Voltage ..............................................................................120V AC

DC Power

Heat Input ..................................................56,000 BTU/hr ± 10%

Fuel Consumption ..................................................0.40 gallon/hr

Power Consumption .........................................108W (maximum)

Zone Heat

Circulation Pumps ...........................................................................................1

Power Consumption (max) ..................................................... 21W

Voltage ............................................................................... 12V DC

Heating Zones

Maximum ......................................................................................1

Domestic Water Heating

Maximum ......................................................................... 1.5 GPM

Physical Specifications

Dimensions (US)...................................26”L x 12.46”W x 17.2”H

Dry Weight ........................................................................... 84lbs.

Wet Weight ......................................................................... 104lbs.

Interlock Switch

The interlock switch is a safety device designed to ensure that the Aqua-Hot’s access cover is securely installed before the burner will operate. Troubleshoot the interlock switch if the following conditions occur:

• The burner fails to operate
• The burner indicator light does not illuminate when the switch is in the ON position

Troubleshooting:

1. Ensure that the boiler tank has sufficiently cooled in order to require heat from the burner.
2. Activate the burner switch located on the interior switch panel.
3. Locate wires #11B and #24 on the wiring harness as they lead into the interlock switch.
4. Disconnect the wires from the switch, noting that wire #24 is connected to the terminal labeled “NO” and #11B is connected to the terminal labeled “COM”.
5. Using an ohmmeter, check the interlock switch for continuity while the switch button is manually depressed.
6. If continuity is not present with the button pressed in, follow the instructions in this section to replace the interlock switch.

Replacement Procedure

1. Disconnect the interlock switch wires by pulling the quick connectors from the switch spade terminals.
2. Release the interlock switch from the Aqua-Hot cabinet by pushing in on the locking tabs and pulling the interlock switch.
3. Remove the defective interlock switch from the AquaHot.
4. Install the replacement interlock switch into the AquaHot ensuring that the locking tabs snap into place.
5. Connect the Aqua-Hot’s replacement wires to the replacement interlock switch with wire #24 connected to the terminal labeled “NO” and wire #11B connected to the terminal labeled “COM”.

Fluid Level Sensor

Introduction:

The fluid level sensor monitors the current fluid level within the Aqua-Hot. This device is intended as a fail-safe measure which will disengage the Aqua-Hot if the fluid ever drops below a set threshold. The fluid level sensor is located on the expansion bottle, which is mounted to the side of the unit (see below).

If the fluid level sensor is malfunctioning, the Aqua-Hot will show no signs of operation whatsoever. Troubleshoot this sensor if there is an adequate amount of fluid present within the Aqua-Hot, and the unit does not operate:

• The burner fails to operate
• The burner switch indicator light fails to illuminate
• The electric element fails to operate
• The indicator light on the electric switch does not illuminate

Troubleshooting Guidelines:

Before troubleshooting the fluid level sensor, ensure that the following requirements have been met.

• The fluid expansion bottle is filled to at least the “COLD” mark.
• Verify that all coach-side in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.  
• Ensure that AC electrical power is supplied to the AquaHot’s electric element.
• Ensure that the fluid level sensor is oriented correctly (see below).

If any of the requirements above are not fulfilled, correct them before continuing to diagnose the fluid level sensor. Reference the troubleshooting guide below.

Troubleshooting Procedure:

1. Verify that the Aqua-Hot’s expansion bottle is full of antifreeze and water heating solution.
2. Verify that the wiring is secure, and in good working condition.
3. Locate the wiring harness for the unit. Find wires #10, #15, and #16. Wires #10 and #15 will co-terminate in a yellow connector.
4. Disconnect these wires from th expansion bottle, and test for continuity across the expansion bottle sensor.
5. If the bottle contains fluid and continuity does not exist across the fluid level sensor, the sensor will need to be replaced.

Replacement Procedure:

In order to replace the fluid level sensor, the overflow bottle must also be replaced. Please visit www.aquahot.com or call 574-AIR-XCEL (574-247-9235) to order the expansion bottle kit. Once you have the replacement part in hand, follow the procedure below.

1. Locate the fluid expansion bottle.
2. Clamp the overflow hose as close to the bottom fitting as possible.
3. Grab a bucket or drain receptacle and place it directly under the lower fitting of the expansion bottle.
4. Remove the clamp from the lower fitting of the expansion bottle.
5. Remove the hose and allow the excess fluid to drain into the bucket.
6. Remove the overflow hose from the upper fitting of the expansion bottle.
7. Remove the old expansion bottle, disconnect the Faston connectors, and discard the old bottle. 
8. Secure the new bottle in position.
9. Crimp the new faston connectors to the new fluid level sensor.
10. Connect these wires to their receptacles on the Aqua-Hot harness.
11. Reconnect the overflow hose to the upper fitting.
12. Reconnect the expansion hose to the lower fitting.
13. Fill the bottle with the previously drained fluid.
14. Remove the hose clamps.
15. Test the Aqua-Hot for normal functionality.

Control Thermostat

The control thermostat is installed into the Aqua-Hot’s boiler tank and monitors the temperature of the antifreeze and water heating solution to determine when it is at operating temperature and when it requires heat. The Aqua-Hot is considered to be at operating temperature between 155°F and 188°F. Please reference Page 10 for the relay control board LED indicator information.

Troubleshooting Conditions:

Troubleshoot the control thermostat if one of the following conditions has occurred:

• There is a lack of hot domestic water and/or interior heat.
• The orange heating status light (D1) does not illuminate while the unit is below 175°F.

Troubleshooting:

1. Verify the following before troubleshooting the control thermostat:

• The Interlock Switch is depressed (access cover is properly installed).
• The overflow bottle is adequately filled.
• The High-Limit Thermostats are not tripped.
• Fuses in the relay control board are functional.

2. Turn the burner and/or electric element switch to the ON position.
3. Check the relay control board to ensure that “Electric Heating Element Status” (D2) and/or “Burner Status” (D5) indicator light is illuminated.
4. Verify that the “Heating Status” (D1) indicator light on the relay control board is illuminated as it should be whenever the Aqua-Hot is below 175°F.

If the “Heating Status” (D1) indicator light is not illuminated, check the following:

• Verify that the temperature of the boiler tank has fallen below the 175°F minimum operating temperature by checking with an infrared thermometer. Take the reading within 12 inches from the painted tank surface with the thermometer set to “High Emissivity” or similar. Do not attempt to take readings on a shiny surface.
• If below 175°F, disconnect the control thermostat’s wires from their connection. Using an ohmmeter, check for continuity across the control thermostat.

If continuity does not exist across the control thermostat under these conditions, follow the directions in this section for replacing the control thermostat. If continuity exists across this thermostat, inspect it, and the wiring harness for any damage.

Control Thermostat Replacement Procedure

1. Ensure that the Aqua-Hot has been completely shut down, all power sources disconnected, and the unit has been allowed to cool completely.
2. Clamp the hoses indicated below with pinch off pliers to prevent drainage of the heating zone loop.
3. Drain one gallon of antifreeze and water heating solution into an external contained to be reused later.
4. Disconnect the defective control thermostat wires by separating the quick disconnect terminals.
5. Using a ⅞” deep wall socket, unscrew the control thermostat from the Aqua-Hot’s boiler tank.
6. Wrap the threads of the replacement control thermostat with 6 wraps of thread seal tape.
7. Reconnect wire #14A and wire #23 to the new control thermostat.
8. Refill the Aqua-Hot’s boiler tank with the previously drained antifreeze and water heating solution.
9. Refill the Aqua-Hot using an external fill pump, filling through the zone fill.
10. Test the Aqua-Hot for normal operation.
11. Test the interior heating loop to ensure that there are no air pockets trapped within the interior heating loop.
12. If necessary, purge the interior heating loop according to the guide on Page 85.

AC High-Limit Thermostat

Introduction:

The AC high-limit thermostat serves as a safety measure in the event that the electric heating element continues to operate after the maximum operating temperature has been reached. The high-limit thermostat allows the current for the heating element to pass through until the boiler tank reaches a temperature of 215°F. Should this temperature be reached, the high-limit thermostat blocks the current to the element, preventing the element to continue to operate.

Note: If the high-limit thermostat is tripped, it is recommended to test the control thermostat and AC relay for proper operation.

Begin troubleshooting the AC High-Limit Thermostat if the electric element fails to operate correctly.

Troubleshooting Guidelines:

The following conditions must be met before the AC High-Limit Thermostat can be diagnosed, and if necessary, repaired.

• The fluid expansion bottle is filled to at least the “COLD” mark.
• Verify that all in-line fuses are functional. • Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the Aqua-Hot’s electric element.

If any of the above conditions are not met, correct them before continuing with troubleshooting. Results of the troubleshooting procedure cannot be verified if the conditions listed above are not fulfilled.

Troubleshooting Procedure:

1. Verify the following before troubleshooting the AC high-limit thermostat:

• The control thermostat is calling for heat.
• The interlock switch is depressed.
• The overflow bottle is adequately filled.
• The high-limit thermostats are not tripped.
• The fuses in the relay control board are functional.

2. Ensure that the unit has been shut down and completely cooled before continuing.
3. Shut off the coach-side power breaker to the Aqua-Hot.
4. Disconnect the 3-pin AC Molex plug from the AC relay enclosure. Leave the DC power supply connected.
5. Activate the “ELECTRIC” switch on the switch panel inside the coach.
6. Using a multimeter, test for continuity across the AC highlimit thermostat by placing one lead on the unit-side Molex connection as shown below.

7. If no continuity exists, locate the AC high-limit thermostat and depress the center button to reset it. Retest for continuity.

8. Move the electric switch to the OFF position. Reset for continuity. If continuity still exists, replace the AC relay.

Replacement Procedure:

If it has been determined that the high-limit thermostat needs to be replaced, it can be easily replaced by following the directions below.

1. Shut off gas, electric, and water supply to the Aqua-Hot.
2. Disconnect the domestic water inlet and outlet line fittings from the Aqua-Hot.
3. Unscrew the nut that affixes the mixing valve to the left side of the Aqua-Hot cabinet wall.

4. Push down on the mixing valve to expose access to the AC high-limit thermostat.
5. Cut the wire tie which wraps the wires on the left side of the unit.
6. Cut the black wires on the AC high-limit thermostat as close as possible to the body of the thermostat and strip the other end.
7. Remove the faulty high-limit thermostat using a ⅝” socket or crow’s foot.
8. Butt-splice a new AC high-limit thermostat to the stripped wire.
9. Reinstall the AC high-limit thermostat using a ⅝” socket or crow’s foot.
10. Re-secure the wires using the extra wire tie provided and reinstall the mixing valve assembly.
11. Make sure the replacement AC high-limit thermostat is functioning properly by testing for continuity across this thermostat.
12. Reposition the tempering valve assembly onto its mounting stud on the left cabinet wall.
13. Re-secure the tempering valve assembly with the previously removed nut.
14. Reconnect the domestic water connections to the PEX fittings of the tempering valve assembly.
15. Reestablish the gas, electric, and water supply to the AquaHot.
16. Test for unit for normal operation.

Burner High-Limit Thermostats

Introduction:

The burner high-limit thermostats serve as a safety measure in the event that the burner continues to operate after the maximum operating temperature (215°F) has been reached.

If the system reaches an over-temperature condition by interrupting the fuel solenoid, preventing diesel fuel from entering the combustion chamber.

Begin troubleshooting the High-Limit Thermostats if the following conditions have occurred:

• The fuel solenoid fails to operate.

Note: If the high-limit thermostat continues to trip, troubleshoot the control thermostat and verify that the boiler tank is full of antifreeze and water heating solution.

Troubleshooting Guidelines:

The following conditions must be met before the AC HighLimit Thermostat can be diagnosed, and if necessary, repaired.

• The fluid expansion bottle is filled to at least the “COLD” mark.
• Verify that all in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the AquaHot’s electric element.

If any of the above conditions are not met, correct them before continuing with troubleshooting. Results of the troubleshooting procedure cannot be verified if the conditions listed above are not fulfilled.

Troubleshooting Procedure:

1. Locate the high-limit thermostats (see Figure 24).
2. Disconnect the burner thermostats using the information below:

• Jumper wire and wire #32 (left) or wires #33 and jumper wire (right)

3. Place a jumper wire between the two wires on the harness to bypass the high-limit thermostat. Check the Aqua-Hot for normal operation.
4. Disconnect the DC high-limit thermostat wires, then, using an ohmmeter, check the thermostat for continuity.
5. If continuity does not exist, depress the button in the center of the thermostat to reset. Reset for continuity.
6. If the thermostat at this point still does not have continuity, follow the instructions in this section to replace the thermostat.

Replacement Procedure:

1. Ensure that the Aqua-Hot has been completely shut down, all power sources disconnected, and the unit is allowed to cool completely before continuing.
2. Remove the two wires from the defective high-limit thermostat.
3. Using a ⅝” socket or crow’s foot, remove the defective high-limit thermostat from the face of the tank.
4. Install the replacement high-limit thermostat into the port on the face of the boiler tank and finger-tighten into place.
5. Reconnect Jumper wire and wire #32 (left) and/or wires #33 and jumper wire (right) to the high-limit thermostat which has just been replaced.
6. Test for normal operation.

Low-Temperature Cutoff Thermostat

Introduction:

The Low-Temperature Cutoff Thermostat (LTCO) operates the domestic hot water priority system by blocking the interior heating feature when domestic hot water is being used. This ensures that even heat is provided for domestic hot water, which avoids the possibility of cold water pockets during showers and other heavy-load applications. Ensure the Aqua-Hot is up to temperature before troubleshooting the Low-Temperature Cutoff Thermostat.

Troubleshooting Condition:

This thermostat should be diagnosed if there is a lack of interior heat or hot water, the D4 light is not illuminated, and the tank is up to operating temperature.

Troubleshooting Procedure:

Use the following troubleshooting tree to diagnose the LowTemperature Cutoff Thermostat.

1. Verify the following before troubleshooting the lowtemperature cutoff thermostat.

• The control thermostat is calling for heat
• The interlock switch is depressed
• The overflow bottle is adequately filled
• The high-limit thermostats are not tripped
• The fuses on the relay board are functional

2. Determine if the unit is ready to provide heat by verifying that the “Low-Temperature Cutoff Status” light is NOT illuminated on the relay control board.

• Verify that the Aqua-Hot is at operating temperature between 155°F and 185°F by using a meat thermometer secured to the tank face.
• Verify that domestic hot water is not being used.

3. If the ‘Low-Temperature Cutoff Status” light on the relay control board is illuminated after the unit has reached operating temperature, complete the following:

• Disconnect wire #14B and #25 from the lowtemperature cutoff thermostat.
• If the light does not go out after disconnecting the low-temperature cutoff thermostat, contact Aqua-Hot Heating Systems for assistance in diagnosing this issue.

Lack of Hot Water

1. If the LTCO indicator light does not illuminate when domestic water is being used or when the Aqua-Hot falls below operating temperature, complete the following:

• Using a temperature sensor, verify that the LTCO thermostat is below 90°F.
• Inspect the wiring to ensure that the Aqua-Hot is wired properly and that the LTCO thermostat has not been disconnected.

2. Disconnect both wires from the Low-Temperature Cutoff Thermostat. Using a jumper wire, connect these two wires together.
3. With the jumper wire installed, check the coach for hot water availability. If after jumping these wires together and hot water has been established, the Low-Temperature Cutoff Thermostat will need to be replaced.

Replacing the Low-Temperature Cutoff Thermostat:

1. Ensure that the Aqua-Hot has been completely shut down and that all the power sources have been disconnected.
2. Locate the Low-Temperature Cutoff Thermostat on the Aqua-Hot.
3. Disconnect the defective LTCO thermostat by separating the quick-disconnect terminals.
4. Using a ⅝” wrench or crow’s foot wrench, remove the defective LTCO thermostat from the Aqua-Hot.
5. Install the replacement LTCO torquing it to 15 in-lbs ONLY. Anything more than 15 in-lbs of torque will damage the thermostat and possibly the unit.
6. Connect wire #14B and wire #25 to the replacement LowTemperature Cutoff Thermostat.
7. Test for normal operation.

Three-Way Valve

Introduction:

The Aqua-Hot has a three-way directional valve to control coolant priority within the unit. This ensures that there will be a supply when heated water is being called for, but can provide interior heating when the need arises.

Troubleshooting Condition:

Troubleshoot the three-way valve if the following conditions have occurred:

• An absence of interior heat
• Inconsistent or complete lack of hot water

Troubleshooting:

1. Verify the following before troubleshooting the three-way valve:

• The control thermostat is calling for heat
• The interlock switch is depressed
• The overflow bottle is adequately filled
• The high-limit thermostats are not tripped
• The fuses on the relay board are functional

2. Verify that the heating zone is operating properly by checking the hoses to see if they are hot to the touch when a heating zone is calling for heat.
3. Locate the relay control board and ensure that both the heating zone status (D6) and the pump status (D3) indicator lights are illuminated.

• Verify that the line on the valve display window is vertical when interior heat is being called for. If this is not occurring, check the LTCO thermostat for functionality (reference Page 22).
• Verify that the line on the valve display window is horizontal when hot water is being requested. This is known as “stir” mode.

4. Ensure that the modes change between interior heat (vertical) and hot water (horizontal), and verify that it matches the relay control board lights. D6 should illuminate while the sight glass is vertical.

5. Locate the wires traveling from the three-way valve as listed below:

• The wires of the three-way valve will terminate at the 16-pin plug of the relay control board.

Note: The following tests (step 6 & 7) will verify functionality of the internal workings of the three-way valve with power directly applied. The valve should actuate, and the sight glass should rotate with at least one of the following tests.

7. Apply 12V DC power to the red wire, and attach a ground wire to the green/black wire. The motor within the threeway valve should activate, rotating the red line in the sight glass vertically (Figure 28a).
8. Apply 12V DC power to the green/black wire, and attach a ground wire to the red wire. The motor within the threeway valve should activate, rotating the red line in the sight glass horizontally into “stir” mode (Figure 28b).
9. If the three-way valve does not function in either of the above tests, it will need to be replaced. Follow the instructions on the next page to replace this component.

Replacement Procedure:

1. Ensure that the Aqua-Hot has been completely shut down, all power sources have been disconnected, and the unit has completely cooled.
2. Use clamp hose pliers to pinch tubing surrounding the three-way valve as indicated in Figure 30.
3. Remove the valve wires from the green connector plugged into the relay control board.
4. Using constant tension pliers, loosen and slide back the constant tension clamps securing the hose to the defective valve.
5. Remove the hose from the defective valve as shown in Figure 31.
6. Remove the two remaining hoses from the defective threeway valve.
7. Slide the hoses onto the valve and set the constant tension clamps back into place.
8. Install the replacement three-way valve according to the specific instructions below related to your unit.

• Reconnect the red wire to Pin #7, and the green wire to Pin #8 of the relay control board connector.
• Crimp a female 22-18AWG “Faston” connector to the green/black wire of the three-way valve. Connect to wire #22 “Faston” connector.

9. Refill the Aqua-Hot’s boiler tank, purging the heating loop if necessary.

Tempering Valve

Introduction:

The tempering valve of the Aqua-Hot mixes the heated domestic water from the boiler tank with cold incoming domestic water at a preset ratio to deliver steady hot water and reduce the risk of scalding. It is recommended that you review the “Lack of Hot Water Troubleshooting Guide” prior to diagnosing the tempering valve.

Troubleshooting Condition:

Troubleshoot the tempering valve if the following conditions have occurred:

• A lack of hot water.
• Hot water supply is uneven.
• Hot water is too hot.
• The D4 light is not illuminated.

Troubleshooting Condition:

1. Inspect the tempering valve to ensure that it is not leaking.
2. Activate the burner and allow the unit to heat unit the burner shuts off. This test cannot to be accomplished with the electric element.
3. Open the hot water valve on an interior faucet without a hot-stop and allow the temperature to stabilize at its hottest point.
4. Using a meat thermometer, take temperature reading of the water. It should be between 115°F and 120°F. Be aware that a water source temperature of less than 65°F may prevent hot water from reaching this threshold.
5. Test the tempering valve’s functionality by turning the knob (see Figure 32). If the knob does not rotate, this tempering valve will need to be replaced. On newer heaters, it will be necessary to remove a black plastic cap from the body of the tempering valve.
6. While running water, if the inlet pipe is excessively hot while the outlet is lukewarm and adjusting the mixing valve results in no change, it may be a faulty mixing valve.
7. If adjustment of the mixing valve is able to effect change in temperature, it must be continually adjusted until the output range of the hot water is between 115°F and 120°F.

Note: Adjusting the mixing valve beyond 120°F will result in a lack of hot water and may result in scalding. Do NOT attempt to adjust the tempering valve without assistance from Aqua-Hot Technical Support or a qualified Aqua-Hot technician.

Replacement Procedure:

1. Turn off the coach water supply.
2. Drain the water pressure by opening the faucets and allowing the water to drain.
3. Disconnect the coach water lines from the tempering valve assembly.
4. Disconnect the PEX pipe fittings from the tempering valve assembly.
5. Remove the pressure relief valve assembly from the tempering valve assembly.
6. Using a back-up wrench, unscrew the tempering valve from the Aqua-Hot. Failure to use a back-up wrench could result in damage to the cold water inlet pipe.
7. Remove the brass fittings from the defective tempering valve.
8. Install the brass fitting onto the replacement tempering valve. Use thread seal on the fittings.
9. Install the replacement tempering valve onto the AquaHot using the back-up wrench to tighten.
10. Install the pressure relief valve onto the replacement tempering valve. Use thread seal tape.
11. Reconnect the PEX pipe and fittings onto the replacement tempering valve. Use thread seal tape. Be sure to inspect rubber seals and replace is necessary.
12. Reconnect the water lines to the tempering valve.

Circulation and Stir Pump

Introduction:

The fluid circulation pump operates to provide fluid circulation to either the interior heating zone or the antifreeze boiler tank depending on the heating and hot water needs at the time. It is used when interior heat is demanded by circulating propylene-glycol and water through the heating loop. It is used to stir the fluid mixture in the tank to ensure optimal hot water performance. The pump will also circulate the tank fluid while the burner cycles on to ensure that the tank is completely and evenly heated during a normal operating cycle.

Troubleshooting Condition:

Troubleshoot the circulation pump if the following conditions have occurred:

• A lack of interior heat.
• Lack of hot water or supply is uneven.

Troubleshooting Procedure:

Follow the procedure to diagnose the fluid circulation pump.

1. Verify the following before troubleshooting the circulation and stir pump:
2. Activate an interior zone for heating and the burner switch. Locate light D6 on the relay control board.
3. Light D6 should illuminate and the circulation pump should begin operating.
4. If the circulation pump still does not operate, locate wire #20 on the wire harness, and apply 12V DC current directly to the pump.

• If the pump operates with 12V DC applied, begin diagnosing the relay control board.
• If the pump does not operate with 12V DC directly applied to it, the pump will need to be replaced.

Replacement Procedure:

1. Ensure that the Aqua-Hot has been completely shut down, all power sources have been disconnected, and that the unit has been allowed to cool completely.
2. Clamp the zone outlet, and the zone return with hose pinchpliers as shown below.
3. Drain the antifreeze and water heating solution from the Aqua-Hot’s boiler tank using the drain valve.
4. Disconnect the defective pump’s wires by removing the electrical plug from the pump body.
5. Using constant tension pliers, loosen and slide back the constant tension clamps securing the hoses to the circulation pump.
6. Remove the hoses from the defective circulation pump.
7. Set the defective pump aside, and put the replacement pump in the same position.
8. Slide the hoses back onto the replacement pump and set the constant tension clamps back into place.
9. Connect the wires to the replacement pump.
10. Refill the boiler tank with a 50/50 mixture of propylene glycol and distilled water.
11. Once the tank has been filled, purge the heating zones by directly connecting the fluid pump to 12V DC power for at least 20 minutes.

AC Electric System

Introduction:

The AC Electric system of the Aqua-Hot 200 Series unit functions to provide supplementary heat to the Aqua-Hot boiler tank. This is done with an electric element, an electric relay, and a DC “control circuit” which engages the electric element when determined necessary by the control thermostat and the relay control board. The electric heating element is not intended to serve as the sole heating source of the Aqua-Hot. The AC electric system will provide enough heat for hand washing, and to maintain tank temperature. Any greater applications require the use of the diesel burner.

Troubleshooting Condition:

Troubleshoot the AC Electric system if the electric element is not functioning properly. This can be verified with a simple, but rather lengthy, test outlined below.

The following conditions must be met before the AC Electric system can be diagnosed, and if necessary, repaired.

• The fluid expansion bottle is filled to at least the “COLD” mark.
• Verify that all in-line fuses are functional.
• Ensure that the unit is completely cool.
• Ensure that DC electrical power is supplied to the Aqua-Hot.
• Ensure that AC electrical power is supplied to the element.
• Verify the thermostats are in working order.

If any of the above conditions are not met, correct them before continuing with troubleshooting. Results of the troubleshooting procedure cannot be verified if the conditions listed above are not fulfilled.

Verify Functionality:

1. Switch both the electric and the burner switches to the OFF position.
2. Allow the unit to cool completely.
3. Verify that the Aqua-Hot is connected to an AC power source such as shore power or an AC generator.
4. Using an infrared thermometer take the temperature of the tank face. The thermometer should be 12” away from the tank face and set to “high emissivity”. Record this temperature on a notepad.
5. Move only the electric switch on the panel to the ON position.
6. Verify that the D2 light on the relay control board is active.
7. After an hour, take another temperature reading on the tank face. If the temperature of the tank face has risen, the electric element is correctly operating.

If through the above procedure it’s been determined that the electric element is not functioning properly, follow the instructions below to troubleshoot.

Troubleshooting:

1. Verify the following before troubleshooting the AC Electric System:

• The control thermostat is calling for heat
• The interlock switch is depressed
• The overflow bottle is adequately filled
• The AC high-limit thermostat is not tripped
• The fuses on the relay board are functional

2. Install a jumper wire on wires #26 and #15. This will circumvent the electric element switch and should cause the electric element to activate.

• If the electric element status indicator light, DC illuminates on the relay control board with the jumper wire installed, troubleshoot the electric element switch on the interior switch panel.
• If the electric element status indicator light does not illuminate when the jumper wire is installed, verify that the fluid expansion bottle is adequately filled, and that the fuse in FH2 is still functional.
• Check the Aqua-Hot’s boiler tank temperature. If the tank temperature is below 155°F and the electric element status light D2 is not illuminated, begin troubleshooting the control thermostat.

3. Verify that the relay control board is sending 12V DC power to the AC relay. Using a voltmeter, test wire #28 for 12V DC power.

• If 12V DC is not present while the electric element switch is in the ON position, and the D2 light is active, the relay control board will need to be replaced.
• If 12V DC power is present at wire #28, disassemble the AC relay enclosure and check for power at Pin #1 of the AC relay. If power is not present at Pin #1, inspect the wiring harness for damage.

4. If 12V DC is present at Pin #1 (wire #28) of the AC relay, complete the following:

• Turn off all coach-side breakers providing power to the Aqua-Hot, then disconnect the Molex plug AC connection.
• Using an ohmmeter, check for continuity across wires #1 and #4 of the AC relay.

If no continuity exists at this point, the relay must be replaced.

5. Verify that the electric heating element is receiving adequate AC power by completing the following:

• Plug the coach into shore power or turn on the generator.
• Using an AC voltmeter, verify that 110V AC are present at the Molex plug connected to the Aqua-Hot. If there is not 110V at this plug, there is a problem with the coach-side power.
• Using a digital clamp-meter, verify the electric element is drawing between 8A and 8.5A.

6. Verify that the electric element has the proper resistance:

• Disconnect the AC Molex plug from the 250 AC enclosure.
• Move the electric switch on the interior switch panel to the ON position. Using an ohmmeter, test for resistance on the white and black terminals of the Aqua-Hot Molex terminal.
• Resistance should be between approximately 11-13 ohms. If there are less than 11 ohms of resistance, the electric element can cause the coach-side breaker to trip (reference Figure 38).

Replacement Procedure:

1. Ensure that the Aqua-Hot has been completely shut down and all power sources have been disconnected. Be sure the boiler tank is completely cooled.
2. Using hose pinch-off pliers, clamp off the heating zone inlet and outlet ports.
3. Drain the antifreeze and water solution from the Aqua-Hot’s boiler tank into an external container to be reused.
4. Remove the two wires secured to the defective electric heating element by releasing the screw terminals.
5. Using a 1-½” (38mm) socket, remove the defective heating element from the Aqua-Hot’s boiler tank.
6. Use 6 wraps of Teflon tape and pipe dope around the threads of the new electric element to ensure that it forms an adequate seal.
7. Install the replacement 1kW electric element into the boiler tank and secure it with the 1-½” (38mm) socket.
8. Reconnect the wires previously disconnected from the electric heating element and tighten the screw terminals.
9. Refill the Aqua-Hot boiler tank with the previously drained fluid, add more 50/50 mix of propylene glycol and distilled water to the tank if needed.
10. If necessary, purge the heat exchanger lines to remove any and all air from the system by running the fluid circulation pump for 20 minutes.

Diesel Burner Schematics

Diesel Burner Operational Flow Chart

Diesel Burner Operation 

Detaching the Diesel Burner

Step 1: Turn off the diesel switch

• Light on the interior switch panel should turn OFF when switch is turned to OFF. Or the burner status should show OFF on the coach interior control panel.

Step 2: Remove the Access Cover

Locate the bolts securing the access cover in place, unscrew the bolts.

Remove the access cover.

Step 3: Disconnect the Diesel Burner’s Controller

Locate the controller and disconnect both plugs.

Step 4: Remove the fuel lines from the Aqua-Hot

Locate where the fuel lines on the diesel burner connect to the Aqua-Hot bulkhead fittings.

Using a 7/16” wrench, loosen the nuts securing each fuel line to the Aqua-Hot.

Step 5: Remove the Diesel Burner from the Aqua-Hot

The diesel burner is secured to the Aqua-Hot with two nuts that can be loosened, and swung out of the way by using a 10mm socket wrench with a 10” long extension.

Carefully pull the diesel burner away from the Aqua-Hot 4 to 5 inches before rotating the burner up, and then remove.

Reattaching the Diesel Burner 

Step 1: Reattach the Diesel Burner to the Aqua-Hot

The diesel burner is secured to the Aqua-Hot with two eye-bolt nuts that can be swung into place, after the diesel burner has been properly aligned and set in place.

The eye-bolt nuts can then be tightened by using a 10mm socket with a 10 inch long extension. Use extreme caution when tightening down the eye-bolt nuts. Over-tightening the eye-bolt nuts can cause the aluminum blower casing to crack. (Torque Specifications are approximately 20-40 in-lbs.)

Step 2: Reattach the fuel lines to the Aqua-Hot

Align the fuel lines on the diesel burner with the fittings on the Aqua-Hot, and using a 7/16” wrench, tighten down both the supply and return fuel fittings.

Step 3: Reconnect the Controller and Mount

Locate the diesel burner’s Controller and connect both plugs that were previously disconnected.

Step 4: Reinstall the Access Cover

Reinstall the Aqua-Hot’s access cover and securely tighten the three bolts securing the access cover in place.

 

Diesel Burner Motor

The diesel burner motor drives the combustion air blower and the fuel pump. In order to perform the following procedures, it may necessary to detach the diesel burner head.

Note: The Aqua-Hot 200 Series is equipped with a 20A Fast Blow Fuse, located on the #3 wire, between the Aqua-Hot main plug and diesel burner controller’s B-plug Pin 4, which is the diesel burner’s motor power wire. Reference Figure 64.

Troubleshooting Procedure:

1. Locate the diesel burner controller’s C-plug and insert the probes of a DC voltmeter into the C-2 (+) and the C-5 (-) locations.

• Turn the burner switch ON and verify the burner status (D5) and heating status lights (D1) are illuminated on the relay control board.

• Observe the voltage level. If a normal voltage range registers on the voltmeter and the motor is not operating, inspect the C-plug harness for any loose or damaged wire connections. If the C-plug harness and connections are in good condition and the motor is not in operation, the motor must be replaced.

If there is not 12V DC present on the C-2 pin, continue with the troubleshooting procedure.

2. Verify the controller is sending power to the diesel burner motor.

• Using a voltmeter, check for 12V DC on the controller B-plug pin 4. If no power, verify the controller is receiving power from the batteries.

Note: The motor may have a flat spot and will cause the burner to work intermittently. When testing the motor, be sure to test it multiple times to find the intermittent problem.

• Using a voltmeter, check for 12V DC on the main plug pin 1 (wire #3). If no power is present, verify the plug is receiving power and there is no damage to wires or the plug.

RPM Test:

1. Disconnect the ignition cables from the ignition electrodes.
2. Remove the four ignition coil screws that secure the ignition coil to the protection cap.
3. Lift the ignition coil and disconnect its wires from the C-plug harness prior to removing completely.
4. Remove the protection cap from the diesel burner so that the motor and clutch halves are exposed.
5. Place a few wraps of black electrical tape around the clutch halves, and then place a small piece of reflective tape over the black tape.
6. Disconnect the motor’s black (+) and brown (-) wires from the C-plug harness’ black (+) and brown (-) wires.  
7. Connect the motor’s wires directly to a 12V DC power supply.
8. Turn the power supply ON and use a photo-tachometer to test for a proper RPM reading.
9. At approximately 12V DC, the RPM reading should be 4500 RPM’s (±300 RPM). If the motor’s RPM reading is not within these specifications, the motor must be replaced.

Motor Replacement Procedure:

1. Follow the directions on Page 41 for detaching the diesel burner.
2. Remove the four ignition coil screws that secure the ignition coil to the protection cap. Lift the ignition coil to disconnect its wires from the C-plug harness prior to removing. Remove the protection cap from the diesel burner so that the motor clutch halves are exposed.
3. Remove the three Hex-Head screws that secure the motor and flange assembly to the blower housing. Remove the motor and flange assembly along with the clutch halves. Disconnect the motor’s black (+) and brown (-) wires from the C-plug harness’ wires.
4. Detach the motor from the motor flange by removing the two Philips heads screws that fasten the two parts together.
5. The motor must be mounted to the flange with the wires and drain hole pointing downward, and the recessed edge of the motor flange pointing upward. This will ensure a proper protection cap fit.
6. Reinstall a clutch half on both the new motor’s shaft and the combustion air blower shaft. Attach the motor and flange assembly, with the recessed edge of the motor flange inline with the wiring access slot of the blower casing to the blower housing with the three Hex-Head screws.
7. Connect the black (+) and the brown (-) wires of the new motor to the C-plug harness pin 8 (+) and pin 5 (-). Feed the C-plug harness’ wires back through the wiring access hole in the protection cap.
8. Reinstall the protection cap. Reconnect the motor’s wires (±).
9. Reinstall the ignition coil and secure to the protection cap with the four ignition coil screws.
10. Follow the directions for reattaching the diesel burner on Page 44.
11. Test for proper operation.

Flame Sensor

The flame sensor is a photo resistive device which supplies the diesel burner’s controller with a DC voltage signal when it detects a flame. When the flame sensor senses the light of the flame, it will shut the ignition coil off, and send a signal to the Controller indicating that everything is working properly. If the flame sensor does not sense the flame, it will shut the diesel burner down in a default after 20 seconds.

Note: In order to perform the following procedures, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching/reattaching procedure starting on Page 41.

Component Test: Ohms

1. Detach the diesel burner.
2. Once the diesel burner has been removed, locate and detach the flame sensor’s green and blue wires from the C-plug harness wires.

3. Connect the flame sensor’s green and blue wires to an ohmmeter.
4. Check resistance by placing a shop rag over the flame sensor’s glass surface, to simulate a no-flame condition. Remove the rag and expose to a light source to simulate a flame condition.
5. If the flame sensor is operating properly, the ohmmeter should register high resistance, over 100K Ω when the glass surface is covered, and less than 200 Ω when exposed to a light source.
6. If these resistance numbers cannot be obtained, verify the flame sensor’s glass sensor is clean. If the flame sensor is clean and the resistance numbers cannot be obtained, the flame sensor must be replaced.

Flame Sensor Maintenance:

1. For light dirt, dust, and/or carbon deposits, simply wipe off the flame sensor with a soft cloth.
2. Should heavy carbon deposits be present, completely remove the flame sensor from the photo disc and clean with brake cleaner.

Flame Sensor Replacement:

1. In order to perform the following procedures, it is necessary to detach the diesel burner head. Be sure to review the detaching/reattaching instructions starting on Page 41.
2. Remove the screw that fastens the flame sensor to the photo disc (as shown in Figure 73), and detach the flame sensor’s green and blue wires from the C-plug harness’ green and violet wires. Remove the defective flame sensor.
3. Slide the tab of the new flame sensor into the provided slot in the photo disc and secure in place with the screw.
4. Connect the flame sensor’s green wire to the green C-plug harness wire (pin 6), and connect the blue wire to the C-plug harness’ violet wire (pin 4).
5. Follow the instructions for reattaching the diesel burner head on Page 44.

Ignition Electrodes

The diesel burner’s ignition coil produces a high voltage ignition spark (approximately 8000 volts) across the ignition electrodes, which ignites the incoming air/fuel mixture.

Note: In order to perform the following procedures, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching/reattaching procedure starting on Page 41.

Cleaning & Maintenance:

1. Polish away any carbon deposits that may have baked onto the metal tips of the ignition electrodes with a coarse sponge.
2. If the ignition electrode’s electrical insulator is cracked or damaged, the ignition electrode must be replaced.

Ignition Electrode Adjustment Procedure:

1. Follow the directions for detaching/reattaching the diesel burner on Page 41.
2. Using a 10mm socket, lightly loosen the retaining clamp bolt.
3. Place the electrode adjustment gauge on the fuel nozzle manifold hex and insert the metal tips of the ignition electrodes into the appropriate notches of the electrode adjustment gauge.
4. Using a 10mm socket, tighten the retaining clamp bolt.
5. Remove the electrode adjustment gauge and reattach to the diesel burner head.

Note: The electrode gauge is mounted to the side of the burner cap. The gauge goes on the fuel nozzle and the tips of the electrodes should be perfectly lined up in the notches.

Replacement Procedure:

1. Using a 10mm socket, loosen and remove the retaining clamp bolt and the retaining clamp.
2. Slide the electrode out of the photo disc.
3. To remove the electrode, hold onto the orange electrode boot, and pull firmly on the electrode.
4. Once the electrode has been removed Inspect inside the orange electrode boot for the retaining clip, which holds the electrode in place. If it is missing, replace the electrode boot.
5. Insert the new electrode into the orange electrode boot, and snap into place. Pull firmly on the electrode to make sure the retaining clip has secured the electrode in place.
6. Slide the electrode into the photo disc.
7. Install retaining clamp and retaining clamp bolt and finger tighten.
8. Follow the ignition electrode adjustment procedure to properly adjust the electrodes.

Note: Be sure not to over-tighten the retaining clamp bolt when readjusting the ignition electrodes. Over-tightening the retaining clamp bolt will bend the retaining clamp and prevent the photo disc from floating freely. Not allowing the photo disc to float freely will cause poor combustion and result in a smoky exhaust. A bent retaining clamp can be re-straightened with a punch and hammer. Lay the clamp’s beveled side down on a solid flat surface and align the thick end of the punch at dead center. Tap the punch lightly until the retaining clamp returns to proper form.

Ignition Coil

The diesel burner’s ignition coil produces a high voltage ignition spark (approximately 8000 volts), which is released across the metal tips on the ignition electrodes during the initial diesel burner start up. Use extreme care when testing the ignition coil, as a High Voltage Shock may result.

Note: In order to perform the following procedures, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching/reattaching procedure starting on Page 41.

Component Test:

1. Remove the four ignition coil screws that secure the ignition coil in place.
2. Disconnect the ignition coil’s black (+) and brown (-) wires from the C-plug harness’ yellow (+) and brown (-) wires.
3. Connect the ignition coil wires directly to a 12V DC power supply (black + wire to + lead and brown - wire to - lead).
4. Turn the power supply ON and watch for a spark to appear across the metal tips of the ignition electrodes. If a spark does not appear, the ignition coil must be replaced.

Note: Some ignition coils are intermittent and will need to be tested numerously. If the ignition coil tests well, and it still will not operate, it is possible there is an issue with the Reporter.

Replacement Procedure:

1. Disconnect the ignition cables from the ignition electrodes. Remove the four ignition coil screws that secure the ignition coil to the protection cap. Lift the ignition coil and disconnect its wires from the C-plug harness wires, prior to removing.
2. Connect the new ignition coil’s black (+) and brown (-) wires to the C-plug harness’ yellow (+) and brown (-) wires. Attach the ignition coil to the protection cap with the four ignition coil screws, then reconnect the ignition cables to the ignition electrodes.
3. Follow the instructions for reattaching the diesel burner and test for proper operation.

Note: If the new ignition coil does not function, check wire connections and ensure they are properly connected and the electrodes are properly adjusted.

Fuel Nozzle

The fuel nozzle is simply a fuel atomizer. It reduces the diesel fuel into a fine spray which is mixed with incoming combustion air, and is ignited within the combustion chamber.

Fuel Nozzle Component Test:

Note: In order to perform the following procedures, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching/reattaching procedure starting on Page 41.

1. Detach the diesel burner.
2. Hook the diesel burner up to an alternate fuel source.

• Disconnect the steel fuel lines from the diesel burner.
• Install the fuel line bypass adapter fitting onto the diesel burner.
• Install rubber fuel lines on both the supply and return fuel pipes, and install the other end of the rubber fuel lines into an adequate supply of diesel fuel. Reference Figure 78.

3. Remove both the ignition cables from the ignition electrodes, or connect a jumper wire (with alligator clips) across the metal tips of the electrodes.
4. Remove the B-plug from the diesel burner’s controller.
5. Turn the diesel switch ON (on the interior switch panel), and plug the B-plug back into the diesel burner’s controller to activate the diesel burner. After approximately 20 seconds, the fuel solenoid will “click” and a fine mist of fuel should appear from the fuel nozzle in a cone-shaped spray pattern.
6. Remove the B-plug from the diesel burner controller.
7. If the cone-shaped spray pattern did not appear, follow the troubleshooting guides for the following components, and verify they are operating properly:

• Fuel Solenoid
• Fuel Pump
• DC High-Limit Thermostats

8. If the components listed above are operating properly, and there is still no fuel coming out of the nozzle, replace the fuel nozzle.

Fuel Nozzle Cleaning and Maintenance:

The fuel nozzle is a precision calibrated part and cannot be cleaned or serviced. A replacement of the fuel nozzle is recommended annually.

Fuel Nozzle Replacement Procedure:

1. Use a ¾” wrench to hold the fuel nozzle stand hex while loosing the fuel nozzle with a ⅝” wrench and remove as shown in Figure 79.
2. When replacing the fuel nozzle, be sure to tighten the nozzle, loosen it a ¼ turn, and then firmly re-tighten. This will establish a seated fit and avoid any leaks.
3. After replacing the fuel nozzle, reattach the diesel burner head.
4. Turn ON the diesel switch for 5 seconds, then turn it OFF. This will activate the diesel burner’s prime-cycle and flush the fuel system of any potential contaminants. Perform this procedure twice.
5. Test for normal operation.

Fuel Solenoid

The fuel solenoid allows the flow of diesel fuel to the diesel burner’s fuel nozzle.

Note: If a long after-smoking condition exists during the diesel burner’s purge cycle, the fuel solenoid valve kit may need to be replaced.

Fuel Solenoid Component Test:

1. Locate and detach the C-plug harness’ violet (+) and brown (-) wires from the fuel solenoid.
2. Connect the (-) lead of a 12V DC power supply to the fuel solenoid’s (-) electrical terminal.
3. Intermittently apply the (+) lead of the power supply to the fuel solenoid’s (+) electrical terminal.
4. Listen for the fuel solenoid to click (open and close).
5. If the fuel solenoid does not click, it must be replaced.

Note: If the fuel solenoid is not working, troubleshoot the diesel burner’s high-limit thermostats (2). If they are tripped, they will not allow the fuel solenoid to operate.

Fuel Solenoid Replacement Procedure:

1. Disconnect the C-plug harness’ violet (+) and brown (-) wires from the fuel solenoid.
2. Using a 8mm wrench, remove the lock nut and flat washer from the end of the fuel solenoid shaft and then pull the fuel solenoid away from the nozzle stand approximately ½”. Remove the fuel solenoid shaft from the nozzle manifold using a 16mm wrench. Discard the shaft and valve kit, as replacements are provided with the new fuel solenoid assembly.
3. Insert the contents of the new fuel solenoid valve kit into the new fuel solenoid shaft. Slide the new fuel solenoid onto the fuel solenoid shaft. Thread the new fuel solenoid shaft with the fuel solenoid to the fuel nozzle manifold and tighten. Secure the fuel solenoid in place with the new flat washer and lock nut.
4. Connect the C-plug harness’ (+) and brown (-) wires to the fuel solenoid’s (+) and (-) electrical terminals.
5. Test for normal operation.

Fuel Pump

The fuel pump draws diesel fuel from the vehicle’s fuel tank and creates a preset pressure of 145 PSI, which is required for proper fuel atomization. Reference the illustration below for a basic overview and understanding of how the fuel pump functions.

Fuel Pump Cleaning and Maintenance:

1. Check all fuel connections for tightness.
2. Check the screen filter located in the fuel supply inlet of the fuel pump for dirt particles. Clean and/or replace if necessary.
3. To adjust the fuel pressure, refer to Page 67 - Fuel pressure check and adjustment.

Fuel Pump Testing Procedure:

1. Clamp off and remove the fuel return and fuel supply lines coming into the Aqua-Hot unit.
2. Attach a short piece of fuel line to both the fuel return and fuel supply ports.
3. Submerse the opposite end of the temporary fuel supply line in a container of diesel fuel.
4. Place the opposite end of the temporary fuel return line in an empty container.
5. Turn the diesel switch ON to activate the diesel burner, and wait ten seconds.
6. If fuel does not flow out of the return line into the empty container, the fuel pump must be replaced,
7. If fuel does flow through the fuel pump when ran off an external source, inspect the following in the coach:

• Check the motor home fuel tank for diesel fuel. If the fuel level is below ¼, the Aqua-Hot diesel burner will not operate.
• Inspect the supply fuel line for any kinks, which would prohibit fuel flow.
• Inspect the supply fuel line for cuts, which would cause the diesel burner to suck air.
• Inspect the fuel filter to make sure all fittings are tight, including hose clamps. Make sure the fuel filter is tight.
• Inspect the Aqua-Hot for loose or cracked fittings.
• Inspect the supply fuel system for loose hose clamps.
• Inspect the fuel pick-up tube in the tank for any loose connections and/or pin holes in the tube.

Fuel Pump Replacement Procedure:

Note: In order to perform the following procedures, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching/reattaching procedure starting on Page 41.

1. Locate and disconnect the C-plug harness wires that connect to the flame sensor and the fuel solenoid. Also, disconnect the ignition cables from the ignition electrodes.
2. Remove the retaining clip that secures the photo disc in place. Gently lift the photo disc so that it releases from the nozzle stand and the ignition electrodes.
3. Loosen the supply and return banjo bolts to remove the fuel supply and return pipes from the fuel pump. Disconnect the high pressure fuel pipe from both the fuel pump and the nozzle stand. Discard the high pressure fuel pipe, gasket rings, and banjo bolts, as replacements are provided in the new fuel pump kit.
4. Remove the four nozzle stand plate screws that secure the nozzle stand plate in place. Remove the nozzle stand plate by pulling on the nozzle stand until the plate releases from the cast-aluminum blower casing.
5. Remove the two pump mounting screws that secure the fuel pump in place. Turn the nozzle stand plate over and remove the snap ring from the fuel pump shaft, using snap ring pliers. Remove the nylon drive gear and then the fuel pump.
6. Attach the new fuel pump to the nozzle stand plate with the two pump mounting screws. Turn the nozzle stand plate over to install the nylon drive gear on the fuel pump’s shaft and secure in place with the snap ring. Dab the teeth of the nylon drive gear with white lithium grease (IsoFlex LDS-18 is recommended).
7. Fit the nozzle stand plate inside the cast-aluminum blower casing and secure in place with the four nozzle stand plate screws. Install the grommets on the fuel return and supply banjo pipes and secure the pipes to the fuel pump with the new banjo bolts and gasket rings.
8. Reconnect the C-plug harness’ violet (+) and brown (-) wires to the fuel solenoid’s (+) and (-) electrical terminals.
9. Insert both the ignition cables into the rubber grommet and slide into the appropriate notch on the blower casing.
10. Reconnect the ignition cables to the ignition electrodes.
11. Reinstall the photo disc and secure it in place with the retaining clip.
12. Reconnect the flame sensor’s green wire to the green C-plug harness and the blue wire to the C-plug harness’ violet wire. Install rubber grommets around the harness wires, and set into place.
13. Follow the directions for reattaching the diesel burner on Page 44.
14. Test for normal operation.

Bearings

The bearings support the combustion air blower’s shaft and allows the blower to turn smoothly.

Bearings Test:

1. In order to perform the following procedure, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching and reattaching section for detaching and reattaching instructions starting on Page 41.
2. Locate and disconnect the C-plug harness wires that connect to the flame sensor and fuel solenoid. Disconnect the ignition cables from th ignition electrodes.
3. Remove the four nozzle stand plate screws that secure the nozzle stand plate in place. Remove the nozzle stand plate by pulling on the nozzle stand until the plate releases from the cast-aluminum blower casing.
4. Remove the four ignition coil screws that secure the ignition coil to the protection cap. Lift the ignition coil and disconnect the black (+) and brown (-) wires from the C-plug harness wires, prior to removing. Remove the protection cap from the diesel burner, so that the motor and clutch halves are exposed.
5. Remove the three hex-head screws that secure the motor and motor flange to the blower housing. Remove the motor and flange assembly along with the clutch halves. Disconnect the motor’s black (+) and brown (-) wires from the C-plug harness’ wires.
6. Remove the four blower housing screws that secure the blower housing to the blower casing. Remove the blower housing so that the combustion air blower is exposed.
7. Spin the combustion air blower by hand. Placing one of the clutch halves to the end of the shaft, assists with the spinning of the bearings.
8. If the combustion air blower rotates smoothly, without any friction or noise, the bearings are in proper working condition. If the combustion air blower does not rotate smoothly and/or produces noise, the bearings are worn and must be replaced.

Bearings Replacement:

1. In order to perform the following procedure, it is necessary to detach and reattach the diesel burner head. Be sure to review the detaching and reattaching section on Page 41.
2. Locate and disconnect the C-plug harness wires that connect to the flame sensor and fuel solenoid. Disconnect the ignition cables from the ignition electrodes.
3. Remove the four nozzle stand plate screws that secure the nozzle stand plate in place. Remove the nozzle stand plate by pulling on the nozzle stand until the plate releases from the cast-aluminum blower casing.

4. Remove the four ignition coil screws that secure the ignition coil to the protection cap. Lift the ignition coil and disconnect its black (+) and brown (-) wires from the C-plug harness wires, prior to removing. Remove the protection cap from the diesel burner so that the motor and clutch halves are exposed.
5. Remove the three hex head screws that secure the motor and motor flange to the blower housing. Remove the motor and flange assembly along with the clutch halves. Disconnect the motor’s black (+) and brown (-) wires from the C-plug harness’ wires.
6. Remove the four blower housing screws that secure the blower housing to the blower casing. Remove the blower housing so that the combustion air blower is exposed.
7. Hold side-B (see Figure 89b) of the blower casing and loosen the retaining nut located in side-A of the blower casing. Remove the retaining nut, steel drive gear and thick flat washer from the combustion air blower’s shaft. Lightly tap the threaded end of the shaft so that the combustion air blower can be easily removed from the blower casing.
8. With a pair of snap-ring pliers, remove the snap rings from both side-A and side-B of the blower casing. Push all the contents of the bearing kit out of the blower casing’s bore/bearing cavity. Discard the retaining nut, steel drive gear, snap rings, bearings, spacer tube, and washers, as replacements are provided in the new bearing kit.
9. Install a new snap ring into side-A of the blower casing. Once the snap ring is in place, insert the remaining contents of the new bearing kit into side-B of the blower casing, starting with the wave washer. Secure the bearing kit assembly in place with the remaining snap ring.
10. Inspect the combustion air blower for warping and/or damage. If warping or damage is visible, the combustion air blower must be replaced.
11. Reference Figure 88 for exact placement of the three washers that slide over the threaded end of the combustion air blower’s shaft prior to installation. Failure to follow the correct order and direction of the dished surfaces on the washers will result in a restricted rotation of the combustion air blower.
12. Slide the combustion air blower’s shaft (with the three washers) up through the bearing kit assembly until the threaded portion appears on side-A of the blower casing. Place the new thick flat washer and steel drive gear on the threaded end of the combustion air blower’s shaft. Thread the new retaining nut on the combustion air blower’s shaft until it is finger tight (DO NOT TIGHTEN).
13. Place a feeler gauge between the combustion air blower and the flat surface of the blower casing. Slowly tighten (or loosen) the retaining nut, holding the combustion air blower, until a .018 - .020 gap is achieved. Remove feeler gauge. Reference Figure 89a.
14. Spin the combustion air blower to ensure a friction free rotation.
15. Reattach the blower housing to the blower casing using the four blower housing screws. Reinstall the clutch half on both the motor’s shaft and the combustion air blower’s shaft. Attach the motor and flange assembly, with the recessed edge of the motor flange in-line with the wiring access slot of the blower casing, to the blower housing with the three hex head screws. Reconnect the black (+) and brown (-) wires of the motor to the C-plug harness’ black (+) and brown (-) wires. Feed the C-plug harness’ yellow and brown wires back through the wiring access hole in the protection cap.

16. Reinstall the protection cap. Reconnect the black (+) and brown (-) wires of the ignition coil to the C-plug harness’ yellow (+) and brown (-) wires. Reinstall the ignition coil and secure to the protection cap with the four ignition coil screws. Reconnect the ignition cables to the ignition electrodes.
17. Fit the nozzle stand plate inside the cast aluminum blower casing and secure in place with the four nozzle stand plate screws. Reattach the fuel supply and return lines to the diesel-burner head.
18. Follow the instructions for reattaching the diesel burner, in the detaching/reattaching section in this manual.

Diesel Burner Controller

The diesel burner controller operates all the components of the diesel burner head and safely shuts the heater OFF in the event of an overheat, flame-out, and low voltage condition. It also receives diesel burner operation status signals from the flame sensor, control thermostat, and DC high-limit thermostat.

Note: Before troubleshooting the Diesel Burner Controller, verify that the Burner has voltage at Pin 4 as shown in Figure 119. There will only be voltage on that pin if the relay control board D5 light is illuminated

Component Test:

The following conditions must exist prior to performing the following diesel burner controller circuit tests. If one of the conditions below does not exist, please contact Technical Support at 1 (800) 685-4298 for assistance.

Condition 1:

• A battery voltage level between 11.6-14 Volts DC must be present at the diesel burner controller during all testing. It may be necessary to perform a voltage check to ensure that this condition exists. To perform the voltage check, locate the controller’s B-plug and insert the probes of a DC voltmeter into the B-4 (+) and B-2 (-) pins.

Condition 2:

• A voltage level of between11.6-14 volts must be present at the diesel ON/OFF switch circuit of the diesel burner controller during all testing. It may be necessary to perform a voltage check to ensure that this condition exists. To perform the voltage check, locate the controller’s B-plug and insert the probes of a DC voltmeter into the B-1 (+) and B-2 (-) locations. Turn the diesel burner ON and observe the voltage levels.

Ground Circuit Test:

Locate the controller’s B-plug and C-plug. Insert the probes of a DC voltmeter into the B-4 (+) and C-5 (-) locations and turn the diesel burner ON. If a voltage reading does not register on the voltmeter, the controller must be replaced. If voltage is present, proceed to the next test.

Control Thermostat Circuit Test:

Locate the diesel-burner controller’s B-plug and C-plug. Insert the probes of a DC voltmeter into the C-1 (+) and B-2 (-) locations and turn the diesel switch ON. If a voltage reading does not register on the voltmeter, the diesel-burner controller must be replaced. If voltage is present, proceed to the next circuit test.

DC High-Limit Thermostat Circuit Test:

Locate the diesel-burner controller’s B-plug and C-plug. Insert the probes of a DC voltmeter into the C-4 (+) and B-2 (-) locations and turn the diesel switch ON. If a voltage reading does not register on the voltmeter, the diesel-burner controller must be replaced. If voltage is present, proceed to the next circuit test.

Motor Circuit Test:

Locate the diesel-burner controller’s B-plug and C-plug. Use a jumper wire to make a connection from the C-1 location to the C-7 location. Turn the diesel switch ON and insert the probes of a DC voltmeter into the C-2 (+) and C-5 (-) locations. If no voltage reading registers on the voltmeter, the diesel-burner controller must be replaced. If voltage is present, proceed to the next circuit test.

Note: Be sure to remove the jumper wire that was used to make the connection from the C-1 location to the C-7 location. Failure to do so will result in an overheating condition during normal operation.

Ignition Coil Circuit Test:

Turn the diesel switch OFF and locate the diesel-burner controller’s C-plug. Also, locate the VDC high-limit thermostat and disconnect it’s 2-way male plug from the (white plastic) 6-way female connector. Insert the probes of a DC voltmeter into the C-8 (+) and C-5 (-) locations and turn the diesel switch ON. If a voltage reading does not register on the voltmeter 18-25 seconds after the initial start-up, the diesel-burner controller must be replaced.

Note: Be sure to reconnect the VDC high-limit thermostat’s 2-way male plug to the 6-way female plug. The diesel burner will not ignite during normal operation if the VDC high-limit thermostat is left disconnected.

Replacement Procedure:

1. Disconnect the Aqua-Hot from any and all power sources.
2. Remove the B-plug and C-plug from the controller. Gently slide out the controller from the side of the diesel burner:

3. Slide the new controller onto the side of the diesel burner.
4. Reconnect the B-plug and C-plug.
5. Test for normal operation.

Note: Be sure to install the controller with the plug ports facing downward. Failure to do so will result in moisture collecting in the ports and potential damage to the controller’s internal circuitry.

Aqua-Hot Maintenance Procedure

Step 1: Test Run the Diesel Burner

1. Turn the diesel burner ON, either on the interior switch panel or coach control panel.
2. After the diesel burner has ignited, inspect the exhaust for smoke.
3. Shut the diesel burner off and wait for unit to completely shut down.

Step 2: Replace the Fuel Filter

1. Locate the fuel filter
2. Using hose pinch off pliers, clamp off both fuel lines going to the fuel filter. Reference Figure 108.
3. Remove the old fuel filter. Replace the fuel filter with the proper replacement canister.
4. Remove the hose pinch off pliers.

Step 3: Run the Diesel Burner

1. Turn the diesel burner ON.
2. After the diesel burner has ignited, let it burn for 1-2 minutes to purge the old fuel out of the nozzle holder, to prevent contamination of the replacement nozzle.
3. Shut the diesel burner OFF, and wait for the unit to completely shut off.

Step 4: Remove the Diesel Burner

1. Locate the diesel burner’s controller and disconnect both plugs.
2. Using a 7/16” wrench, loosen the nuts securing each fuel line to the Aqua-Hot.
3. The diesel burner is secured to the Aqua-Hot with two nuts that can be loosened and swung out of the way by using a 10mm socket wrench with a 10 inch long extension.

• Carefully pull the diesel burner away from the AquaHot 4 - 5 inches before rotating the burner, then remove completely as shown in Figure 115.

Step 5: Clean and Inspect the Combustion Chamber and Heat Transfer Tabs

• Remove the combustion chamber by loosening and removing the four nuts, securing the combustion chamber to the boiler tank and pulling it straight out, approximately 16 inches.
• Once the combustion chamber has been removed, use a long handled wire brush, and brush the heat transfer tabs to loosen soot deposits. Failure to do so will reduce the Aqua-Hot’s heat transfer capabilities.

• Inspect the Combustion Chamber assembly and Air Swirler for damage or signs of warping.
• Inspect the outer ring that the photo disc seats against for signs of warping.
• Inspect the back side of the Air Swirler for signs of warping between screws.

Step 6: Reinstall the Combustion Chamber

• Reinstall the Combustion Chamber assembly and the Air Swirler into the Aqua-Hot.

Step 7: Inspect the Diesel Burner

• Reinstall the Combustion Chamber assembly and the Air Swirler into the Aqua-Hot.

Inspect the following:
1. Electrodes Damaged Improperly adjusted	3. Photo Disc Warped Bent	5. Flame Sensor Cracked Overheated (purple color) Melted wires Dirty	7. Broken or cracked “Ears” Due to over-tightening of eye-bolts
2. Fuel Pump Leaks	4. Harness & Ignition Coil Wires Cracked or bare wires Hard or brittle wires	6. Rubber Grommets Hard or brittle Rubber has been cut out Right & left properly positioned

 

Step 8: Clean Ignition Electrodes and Flame Sensor

1. Ignition Electrodes

• Polish away any carbon deposits that may have baked onto the metal tips of the ignition electrodes with a coarse sponger

2. Flame Sensor

• For light dirt, dust, and/or carbon deposits, simply wipe off the flame sensor with a soft cloth.
• Should heavy carbon deposits be present, completely remove the flame sensor from the photo disc and clean with brake cleaner.

Step 9: Replace Fuel Nozzle

• Use a ¾” wrench to hold the fuel nozzle manifold hex, while loosening the fuel nozzle with a ⅝” wrench and remove.
• When replacing the fuel nozzle, be sure to tighten the nozzle, loosen it a ¼ turn, and then firmly re-tighten. This will establish a seated fit and avoid any leaks.

Step 10: Adjust Ignition Electrodes

• Using a 10mm socket, slightly loosen the retaining clamp bolt.
• Place the electrode adjustment gauge on the nozzle manifold hex and insert the metal tips of the ignition electrodes into the appropriate notches of the electrode adjustment gauge.
• Using a 10mm socket, tighten the retaining clamp bolt.
• Remove the electrode adjustment gauge.

Note: Be sure not to over-tighten the retaining clamp bolt when readjusting the ignition electrodes. Overtightening the retaining clamp bolt will bend the retaining clamp and prevent the photo disc from floating freely. Not allowing the photo disc to float freely will cause poor combustion, and result in a smoky exhaust. A bent retaining clamp can be re-straightened with a punch and a hammer. Lay the clamp’s beveled side down on a solid flat surface and align the thick end of the punch at dead center. Tap the punch lightly until the retaining clamp returns to proper form.

Step 11: Inspect the Photo Disc

1. If the photo disc is not free-floating, the electrode clamp bolt has been over-tightened, and has bent the electrode clamp. Using a 10mm socket, remove the electrode clamp and re-straighten.

• Lay the clamp’s beveled side down on a solid flat surface and align the thick end of the punch at dead center. Tap the punch lightly until the retaining clamp returns to proper form.

Step 12: Reinstall the Diesel Burner

• Align the diesel burner with the Aqua-Hot, using the alignment tabs welded on the Aqua-Hot.
• Swing the eye-bolts around the “Ears” on the diesel burner and securely tighten, using a 10mm socket with a 10in long extension.

Step 13: Reconnect the Fuel Lines

• Align the fuel lines on the diesel burner with the fittings on the Aqua-Hot. Using a 7/16” wrench, tighten down both the supply and return fuel fittings.

Step 14: Plug in the Diesel Burner’s Controller and Mount

• Locate the diesel burner’s controller and connect both plugs.

Step 15: Reinstall the Aqua-Hot’s Access Cover

• Reinstall the Aqua-Hot’s access cover.

• Securely tighten the two bolts securing the access cover in place.

Step 16: Test for Normal Operation

• Turn the diesel burner ON and allow the diesel burner to run for a complete cycle, until it shuts off on its own.
• After the diesel burner has shut off, turn on the interior heat or run hot water until the diesel burner cycles back on. When the diesel burner cycles back on, check the exhaust for any signs of smoke.

Lack of, or Uneven, Hot Water

A lack of hot water, or uneven delivery of hot water (hot water that contains cold spots), is typically due to a failure of one more of five components: the shower head, the stir pump, the three-way valve, the low-temperature cutoff thermostat, or the tempering valve.

• Shower Head
  • It is possible that the shower head in the coach is drawing hot water too quickly from the Aqua-Hot, overtaxing the unit resulting in hot water delivery problems. The shower head should be limited at 1.5GPM max.
• Stir Pump
  • Reference Page 27 to troubleshoot the stir pump.
• Three-Way Valve
  • Reference Page 24 to troubleshoot the three-way valve.
• Low-Temperature Cutoff Thermostat
  • Reference Page 22 to troubleshoot this component.
• Tempering Valve
  • Reference Page 26 to troubleshoot the tempering valve.

Once these components have been diagnosed, restart the Aqua-Hot and allow it to heat to operating temperature. Draw hot water to determine if the problem has been addressed.

Lack of Interior Heat

A lack of interior heat with a functioning burner can be attributed to many potential issues in the Aqua-Hot. Diagnosis will involve three stages. Stage 1 will outline common reasons for overall unit non-function that exists outside of the unit. Stage 2 will diagnose common issues inside the unit, including lack of burner operation. Stage 3 will address specific reasons for a lack of interior heat. It is very important that troubleshooting proceed in the order outlined below. The issues most common with a lack of heat are:

• A non-functional three-way valve
• A seized circulation pump
• Air trapped in the coach heating loop
• A malfunctioning low-temperature cutoff thermostat

Stage 1:

• The coach is supplied with power
• The Aqua-Hot has an adequate supply of fuel
• All coach-side fuses are functional and able to supply power
• All water sources connected to the coach are shut off
• All fuses on the relay control board are functional
• The overflow bottle is filled to at least the COLD mark

Stage 2:

• Visually inspect the interior cabinet of the Aqua-Hot unit, searching for any damaged or disconnected wires. Reconnect or repair if necessary.
• The 250-D02 contains a 20A fuse in the wiring harness. Make sure this fuse has not burned out.
• Make sure the high-limit thermostats are not tripped or defective. Replace if necessary.
• Test for unit operation.
  • If the burner fails to operate, follow the procedure on Page 90 to begin diesel burner troubleshooting.

Stage 3: 

1. Begin troubleshooting the three-way valve. See Page 24.
2. Reference Page 22 to diagnose the Low-Temperature Cutoff Thermostat.
3. Locate the circulation pump within the Aqua-Hot cabinet. It should begin operating immediately when the heater starts up. If the pump does not begin to operate, see the procedure on Page 27 for troubleshooting. 
4. Locate all of the heat exchangers within the coach and determine if any of them are outputting heat.

• If at least one heat exchanger is outputting heat, an air bubble may be preventing the flow of the antifreeze and water heating solution.
• It may be possible to resolve this issue by allowing the circulation pump to run continuously, checking the heat exchangers periodically to determine if they have begun to function. See Page 85 for the heating loop purge procedure.

250-D02 Unit Smoke

Purpose:

It is possible that the Aqua-Hot 250-D02 may smoke upon first start-up. There are many possible causes for smoke as listed below.

If the unit has sat for an extended period of time unused, please perform the annual service.

• Clear exhaust or no smoke
  • The unit is operating correctly
• Blue/White smoke
  • Fuel Solenoid
  • Nozzle Tower
  • Control Thermostat
  • Short-cycling
• Black smoke
  • Low voltage
  • Exhaust system damage
  • Air intake
  • Burner is improperly seated
  • Combustion chamber damage
  • Fuel delivery system

As such, it is necessary to select the correct troubleshooting procedure to solve the issue quickly.

Blue/White Smoke

Smoke During Start-Up or Shut-Down:

1. Ensure that the unit is not short-cycling (rapid power-up and shut-down) during its start-up procedure. This can be caused by:

• A faulty switch
• Damaged wiring
• A malfunctioning control thermostat

2. Diagnose the control thermostat by testing for continuity. Reference Page 17 for the procedure. Test the unit after this is complete.
3. Detach the diesel burner from the Aqua-Hot (see Page 41) to gain access to components for testing.
4. Remove the igniter coil flange to gain access to the fuel tower, nozzle, igniter module, and flame sensor.
5. Visually inspect this sub-assembly, looking for any damage or leak locations.

Smoke During the Burn Cycle:

1. It is possible that the electrodes of the igniter module have been knocked out of adjustment.
2. Follow the directions on Page 41 to gain access to the diesel burner head.
3. Using a Webasto electrode gauge, make sure the tips of the electrodes fit into the grooves of the gauge.
4. Air may be present in the fuel system, resulting in the uneven delivery of fuel to the nozzle and causing excessive smoke. Check the fuel delivery system for any damage or loose clamps which may introduce air into the fuel line.
5. Check the ignition coil for proper operation.

Black Smoke:

1. Ensure that the Aqua-Hot is receiving 12V DC power from the coach.
2. Inspect the exhaust system for any damage or restrictions. Remedy these issues.
3. Remove the access cover of the unit.
4. Attempt to shake the burner sub-assembly. If the burner moves, it has been improperly seated. Follow the directions on Page 41 to remove and reinstall the diesel burner.
5. If at this stage the burner is still producing black smoke, it is recommended that the annual service be performed. See Page 75 for the procedure.
6. Visually inspect the inside of the combustion chamber for any warping or apparent heat damage.
7. Remove the diesel burner from the Aqua-Hot - see Page 41.
8. Remove the combustion chamber to gain access to the heat exchanger as shown in Figure 141.
9. Using a wire brush, scrub the heat exchanger inside the Aqua-Hot as shown in Figure 141.
10. If at this stage, black exhaust smoke is not remedied, contact the Aqua-Hot Technical Support at 574-AIR-XCEL (574-247-9235) or locate your nearest authorized service center.