Dometic RV Air Conditioner How to & Troubleshooting Guide

Issues with your RV air conditioner can be frustrating. If the unit is not performing as it should, this can make it uncomfortable for the RV occupants, especially during extreme conditions. The thought of “breaking the bank” to have the problem is another “headache”.

The good news, however, is that many of the issues to do with your RV air conditioner can be resolved by yourself, once you know the right steps required to successfully troubleshoot the unit. In this guide, we are going to show you what you need to do to resolve some common Dometic RV air conditioner issues.

How to Reset Your Dometic RV Air Conditioner

Performing a reset on your comfort control center system removes all previous program memory and resets the system to factory settings. The procedure may be necessary if the comfort control center is not operational, inadequate data, or no functions occur. The factory setting of 72oF for cooling and 68oF for heating modes are entered.

To initiate a reset, follow these steps below:

  1. Turn control on to ensure annunciator data and light are present. If data and light are present, continue to the next step.
  2. Depress MODE switch to activate annunciator light.
  3. Simultaneously depress the bottom two buttons (temperature UP and DOWN) and hold.
  4. While holding these buttons down, depress the MODE button once and release.
  5. Release the two buttons previously held down.
  6. Depress the MODE button once again.
  7. At this time the light should extinguish, and the mode should register “OFF”. If not, repeat steps 2 through 6.
  8. Retest system ensuring that all functions are present and operational.

Why Does My Dometic RV Air Conditioner Keep Shutting Off?

If your RV air conditioner keeps turning on and off, the thermostat may be the problem. A bad thermostat can prevent the signal to the cooling system. Another probable cause for this problem is frayed wiring or your thermostat is not correctly calibrated.

Dometic RV Air Conditioner Error Codes, Their Meaning, and Fixes

Dometic RV air conditioners display various error codes to indicate issues with the unit. Some of the fault codes will display only after the unit is stopped, which is normal and is done where the fault will not interrupt the normal function of the air conditioner.

The following is a list of error codes that you may get and what they actually mean:

  • E1- Room temperature sensor fault

To fix this error, you need to call for service.

  • E2- Evaporator sensor fault

To fix this error, you need to call for service.

  • E3- Communication fault

To fix this error, you need to call for service.

  • E4- Condenser sensor fault

To fix this, call for service.

  • H1- Defrosting instructions

This error code indicates defrosting in progress. Wait for defrost to complete.

Dometic RV Air Conditioner Compressor Not Coming On

If the fan operates but the compressor doesn’t come on and does not hum, this can be caused by several issues. In an attempt to troubleshoot and fix the problem, check the following:

Operation

Operating instructions can vary from one model to another. Be sure you are familiar with the proper operating instructions for the specific model of heat pump you are diagnosing. Check the installation and operating manual that comes packaged with each heat pump system.

Wiring

If the unit’s compressor or fans fails to operate, chances are it is not receiving proper power. Be sure the power cord is plugged in. Also, check the fuses and breakers.

On rooftop units, there is a 6-pin connector. Verify that all wires are tight in this connector and to all components.

Check this too: Why Does My RV Air Conditioner Leak When it Rains?

On some basement units, there are two 9-pin connectors. Verify all wires are tight in each connector and to all components.

Relays

Depending on your model, the relays on these units may be used for different purposes. Below are a few examples:

The time delay relay is used on Model 39424.601. Its purpose is to provide a 30-second delay of power to circuit 2 system after circuit 1 system.

To check the relay:

  • Use a voltmeter. Place one lead of the voltmeter to terminal 1 of relay.
  • 30 seconds later after terminal 1 receives AC volts, move voltmeter lead to terminal 2 of relay. AC volts should be present.

On model 39224.601, the relay is used to complete the 115 volt AC circuit to the compressors, high fan, and low fan. On model 39424.601, it is used to complete 115 volt AC to the reversing valves for circuit 1 and circuit 2. The relay has a DC volt coil. The coil terminals are 1 and 3. When the coil is not energized (no power to terminals 1 and 3), there is no continuity between terminals 4 to 2. When energized (power to terminals 1 and 3), there will be continuity between terminals 4 to 2.

On models 39115.602, 39115.616, and 39115.626, the relay is used to complete 115 volt AC circuits to the compressor and for fan speeds. The relay has a DC volt coil. To check the relay:

  • First verify AC volts have been turned off to the unit.
  • Next, verify the relay coil is not energized (no DC power). There should be no continuity between terminals COM to NO.
  • Energize the coil with DC volts (10 to 16). There should be continuity between terminals COM and NO.
  • If the above checks are correct, the relay is good. Do not replace it.
  • If the previous checks are not correct, the relay is defective and should be replaced.

AC power module

The AC power module consists of relays, dip switches, plug receptacles, and other components. If any of these are defective, the complete control box must be replaced. Replace power module board on units that are not equipped with a replaceable control box. The 3-amp fuse is the only replaceable component.

The board is a signal receiver and completes AC volt circuits according to what signal it receives. Verify configuration operation before troubleshooting the AC power module. Make sure DC volts are within operation range and 115 volts are supplied to the AC power module board.

For rooftop air conditioners, follow these instructions to troubleshoot:

  • To verify circuits are being completed by the AC power module board, you should first disconnect the 6-pin plug connector from the electric kit.
  • Using a 115 volt incandescent bulb, check from terminal 5 (white-common) to the other terminals to determine if a particular circuit is completed through the board. If the circuit is completed, the light will illuminate. Don’t use a voltmeter for these checks as it will give erroneous readings.

If the circuit is completed and the component is not operating, the problem is the rooftop unit or the connection is not being completed through the connector.

Selector switch

For models with mechanical controls, the heat pump has an air distribution box that has a mechanical selector switch and thermostat installed in it. The selector switch has eight positions including “OFF”. This controls fan speed, heating mode, and cooling modes.

The thermostat controls the temperature range from 65oF on the coldest side to 90oF on the warmest side. In the cooling/heating mode, the compressor ON/OFF is controlled by the thermostat setting.

For cooling operation, the blower runs continuously to circulate air and maintain an even temperature. The compressor will come on when cooling is required to maintain the selected temperature level.

Cable assembly

The ten (10) wire cable is used with remote wall-mounted thermostats. It connects the wall-mounted thermostat (bimetal and electronic thermostat assemblies) to the relay board.

To check the cable assembly, disconnect each end of the cable assembly and check for continuity on each wire in the assembly. Also, check each connector for bent pins or loose wires. Each wire has a receptacle that snaps into the connector.

Thermostat

There are four types of thermostats used on Duo-Therm units: Mechanical thermostat, Bimetal thermostat, Analog thermostat, and Comfort Control Center.

The mechanical thermostat used for air conditioners has two terminals. It controls the on and off cycling of the compressor. To check the thermostat for operation:

  • Turn the air conditioner breaker off, and disconnect the wires to the thermostat.
  • Turn the control knob clockwise to cooler. You should have continuity.
  • Turn the thermostat knob counter clockwise to warmer and no continuity should be present.
  • If you have incorrect readings, replace the thermostat.

There are three different analog thermostats being used to control Duo-Therm air conditioners, air conditioners with heat strips, and heat pumps. The type of thermostat used depends on the unit and the accessories used with it. The proper location of the analog thermostat is very important, to ensure that it will provide a comfortable RV temperature.

The Comfort Control Center is the component that makes all decisions for operation depending on the system and the accessories connected to it. If the system is to be used without a remote temperature sensor, the proper location of the Comfort Control Center is very important to ensure that it will provide a comfortable RV temperature. It may be mounted anywhere that is convenient in the coach if the system is to be used with a remote temperature sensor.

To check the Comfort Control Center, follow these instructions:

  • First verify the DC power is being supplied and the polarity is correct. You can do this by plugging the Comfort Control Center communication cable into a standard cable (RJ-11 type) jack.
  • Use a VOM meter and read DC volts between red (+) and black (-). If DC power is not present or reversed polarity, check the communication cable.
  • If DC power is present at the RJ11 plug on the Comfort Control Center, the next step is to perform a reset. If the Comfort Control Center still does not illuminate or the display does not read, replace the Comfort Control Center.
  • If the correct system information does not show, check the configuration before control is replaced.

Fuse

A 3-amp fuse is installed in the analog control box and Comfort Control Center power module to protect the system from shorts or overload created by disconnecting or reconnecting components when DC power is still connected to the system.

To test, remove the fuse and do a continuity check. If there is no continuity, the fuse needs to be replaced. Another test can be done without removing the fuse. Use a DC voltmeter to check between the ground and to each side of the fuse, if there is a voltage on one side only, the fuse is bad and needs to be replaced.

Breaker

The unit is to be protected by a time-delay fuse or HACR (heating, air conditioner, refrigerator) breaker. If your air conditioner is not coming on, the breaker may have tripped. You can determine if the breaker is tripping prematurely by taking an amp reading at the unit AC voltage supply line. Place a clamp-on type ammeter around the black wire between the unit and the breaker. Turn the unit ON and record the amp draw. If the breaker trips before the rated amperage, replace the breaker.

Overload protector

An overload protector is a component that will open the AC circuit to the compressor if the compressor overheats due to an electrical problem. Some compressors have the overload protector built inside the compressor. This type, if defective, requires a complete compressor replacement.

Most compressors have the overload protector mounted on the exterior of the compressor casing. To check this type of protector:

  • Turn the air conditioner circuit breaker OFF.
  • Make sure that the overload is at ambient temperature and measure continuity across its terminals. If open, it should be replaced.
  • A weak overload protector in the electrical system will cause the compressor to start and stop rapidly or short cycle. This situation will be difficult to test. An exact replacement overload protector should be used whenever a replacement is required.

Compressor

To troubleshoot the compressor, follow these steps:

  • Turn the air conditioner circuit breaker to OFF.
  • Disconnect the wires from the COMMON, START and RUN terminals.
  • Using an ohm meter, set it to the lowest ohm scale and check for continuity between all three terminals. Lack of continuity between any of the terminals indicates faulty windings in the compressor, and the compressor should be replaced.
  • Next, scrape some paint off the compressor casing and check for continuity between each terminal and the casing. If you get a reading, the windings are shorted to the casing and the compressor must be replaced.

How to Recharge a Dometic RV Air Conditioner

To properly evacuate and recharge a sealed system, you’ll need the following equipment items:

  • A piercing type clamp-on saddle valve
  • A braze-on processing valve
  • A core removal tool#
  • A process tube fitting
  • A set of compound gauges
  • Vacuum pump
  • Equipment to weigh a precise amount of refrigerant
  • R-22 refrigerant
  • Gas welding equipment
  • R-22 refrigerant leak detector
  • Recapturing or recycling  equipment

To drain the R-22 refrigerant:

  1. Attach a clamp-on saddle valve on the low side process tube. If the air conditioner does not have a low side process tube, attach a saddle valve at the point where you will add a process tube.
  2. Slowly drain the R-22 refrigerant by using recapturing or recycling equipment. Do not leave the clamp-on saddle valve on the unit as it will cause leaks.
  3. If you are going to use the braze-on processing valve, once the refrigerant has been drained, use a tubing cutter and cut the tube near the end. Do this on both the low and high side processing tubes.
  4. Next, weld the process tube in place. We recommended a brazing material which melts between 950oF and 1450oF, and contains a minimum 2-percent silver and 5-percent to 10-percent phosphorus, as it does not require the use of a flux to join copper to copper.
  5. Connect the blue colored low pressure line of the compound gauge to the charging port on the low side pressure tubing. Next, connect the red colored high pressure line of the compound gauges to the charging port on the high side pressure tubing,
  6. Next, connect the yellow colored line of the compound gauges to the charging cylinder and add 2 or more ounces of R-22 refrigerant to the sealed system and check all weld joints for leaks. Let the refrigerant stay in the system for about 10 minutes. If you detect a leak, drain the system and repair the leak before you proceed.
  7. When you are sure the system is sealed, drain any refrigerant from the system and connect the yellow common line of the compound gauges to the vacuum pump.
  8. Open the pressure relief valve on the vacuum pump. This allows the major contaminants from the sealed system to escape into the atmosphere instead of entering the oil in the vacuum pump.
  9. Both the low and high side valves on the compound gauge set should be opened and vacuum pump turned on.
  10. After 5 minutes, close the pressure relief valve on the vacuum pump. Check the blue gauge after running the vacuum pump for 10 minutes. A vacuum reading of 0-10 inches would indicate a leak in the system or the hose connections.
  11. Now the blue low side and the red high side lines should be disconnected. Make sure that the air conditioner connection is sealed before removing the lines. The process tube can be pinched off in two places; the charging port cut off, and the end of the tube brazed for a hermetically sealed system.

Dometic RV Air Conditioner Not Coming On

If your unit does not run; no fan, no compressor, it may be due to several reasons. Check the following:

Operation

Operating instructions can vary from one model to another. Be sure you are familiar with the proper operating instructions for the specific model of air conditioner you are diagnosing. Check the installation and operating manual that comes packaged with each system to make sure you are following proper operating procedures.

Check this too: Coleman RV Air Conditioner How to & Troubleshooting Guide

AC Voltage

The unit is a 115VAC, 60Hz appliance. The proper operating range is between 103 and 126.5 volts AC. The voltage reading should be taken at the unit power supply leads. Perform one test when the unit is turned OFF and another with it running under load. If the voltage is not within the proper operating range, you must correct it before operating the unit.

DC Voltage

On certain electric-controlled air conditioners and heat pump models, DC volts must be supplied to the control board. The operational range is 10 to 16 VDC. If the DC voltage is below 10 VDC, you might experience the improper operation of the components within the mainboard.

Breaker

The unit is to be protected by a time-delay fuse or HACR (heating, air conditioner, refrigerator) breaker. If your air conditioner is not coming on, the breaker may have tripped. You can determine if the breaker is tripping prematurely by taking an amp reading at the unit AC voltage supply line:

  • Place a clamp-on type ammeter around the black wire between the unit and breaker,
  • Turn the unit ON and record the amp draw. If the breaker trips before the rated amperage, replace the breaker.

Wiring

If the unit’s compressor or fans fails to operate, chances are it is not receiving proper power. Be sure the power cord is plugged in. Also, check the fuses and breakers.

On rooftop units, there is a 6-pin connector. Verify that all wires are tight in this connector and to all components.

On some basement units, there are two 9-pin connectors. Verify all wires are tight in each connector and to all components.

Fuse

A 3-amp fuse is installed in the analog control box and Comfort Control Center power module to protect the system from shorts or overload created by disconnecting or reconnecting components when DC power is still connected to the system.

To test, remove the fuse and do a continuity check. If there is no continuity, the fuse needs to be replaced. Another test can be done without removing the fuse. Use a DC voltmeter to check between the ground and to each side of the fuse, if there is the voltage on one side only, the fuse is bad and needs to be replaced.

Thermostat (Analog, Bimetal, Comfort Control Center)

There are four types of thermostats used on Duo-Therm units: Mechanical thermostat, Bimetal thermostat, Analog thermostat, and Comfort Control Center.

The mechanical thermostat used for air conditioners has two terminals. It controls the on and off cycling of the compressor. To check the thermostat for operation:

  • Turn the air conditioner breaker off, and disconnect the wires to the thermostat.
  • Turn the control knob clockwise to cooler. You should have continuity.
  • Turn the thermostat knob counter clockwise to warmer and no continuity should be present.
  • If you have incorrect readings, replace the thermostat.

Cable assembly

The ten (10) wire cable is used with remote wall-mounted thermostats. It connects the wall-mounted thermostat (bimetal and electronic thermostat assemblies) to the relay board.

To check the cable assembly:

  • Disconnect each end of the cable assembly and check for continuity on each wire in the assembly.
  • Also, check each connector for bent pins or loose wires. Each wire has a receptacle that snaps into the connector.

Ambient temperature

Running the air conditioner at a temperature below 75oF Fahrenheit may cause the inside coil (evaporator) to freeze up in the cooling mode. This mostly occurs at night. Even after the ambient temperature has gone up, the coils will remain frozen.

To assist in the defrosting of the coil, follow these instructions:

  • Turn the air conditioner to HI FAN mode; set the temperature selector to a higher setting and let the air conditioner fan run until the coils are defrosted.

Temperatures below 24oF (Comfort Control Center system) or 40oF (mechanical changeover thermostat) will turn off the operation of the heat pump system.  It is recommended the auxiliary heat (furnace) be used if the temperatures are subject to dropping below this outdoor temperature. Running the heat pump at an ambient temperature above 70oF will cause the system amperage to increase. Circuit breakers popping or compressor cycling on overload would be common.

AC power module board

The AC power module consists of relays, dip switches, plug receptacles, and other components. If any of these are defective, the complete control box must be replaced. Replace power module board on units that are not equipped with a replaceable control box. The 3-amp fuse is the only replaceable component.

The board is a signal receiver and completes AC volt circuits according to what signal it receives. Verify configuration operation before troubleshooting the AC power module. Make sure DC volts are within operation range and 115 volts are supplied to the AC power module board.

For rooftop air conditioners, follow these instructions to troubleshoot:

  • To verify circuits are being completed by the AC power module board, you should first disconnect the 6-pin plug connector from the electric kit.
  • Using a 115 volt incandescent bulb, check from terminal 5 (white-common) to the other terminals to determine if a particular circuit is completed through the board. If the circuit is completed, the light will illuminate.
    • Terminal 1 is a blue wire and is the compressor circuit.
    • Terminal 2 is a black wire and is High Fan circuit.
    • Terminal 3 is a yellow wire and is Medium Fan circuit.
    • Terminal 4 is a red wire and is Low Fan circuit.
    • Terminal 5 is a white wire and is Common 115 V.
    • Terminal 6 is a green/yellow wire and is casing ground.

Don’t use a voltmeter for these checks as it will give erroneous readings.

If the circuit is completed and the component is not operating, the problem is the rooftop unit or the connection is not being completed through the connector.

How to Clean a Dometic RV Air Conditioner Filter

For the Dometic rooftop air conditioner brisk 2 It is recommended you periodically( a minimum of every two weeks of operation)remove the return air filter located behind the return air grille and wash it with soap and warm water, allowing it to dry, and then re-install.

Note that you should never run the unit without the air filter in place. Doing so would result in the evaporator becoming blocked with dust and dirt, and may substantially degrade performance over time.

How to Make a Dometic RV Air Conditioner Quieter

Noisy operation (cooling or heating mode) could point to a number of issues. To fix the problem and make your air conditioner quieter, check the following:

Loose parts

Loose parts can cause the air conditioner to operate noisily. Check for any loose bolts, any component rubbing against its housing, or plastic parts that might be cracked. Repair or replace parts as necessary to resolve any noise problems.

Check this too: Norcold RV Fridge How to and Troubleshooting Guide

Fan blade

The blower motor will have either a squirrel-cage or blade-type fan attached to it. Turn the air conditioner circuit breaker to OFF. Adjust the component to make sure it is not rubbing against its housing or any plastic parts which might be cracked. Repair or replace parts as necessary to resolve any noise problems.

Tubing vibration

If any of the copper tubings is rubbing against itself or any other part, replace or position tubing as necessary.

Reversing valve

The reversing valve is the heart of the heat pump. It directs refrigerant flow to the coils to achieve proper direction of flow that allows the same system to supply heated or cooled air to enter the inside atmosphere of the structure according to occupants’ desires. The reversing valve’s solenoid can be energized in either heat or cool mode of operation, depending on the type of unit you have.

The solenoid on the reversing valve can be loose, which causes a humming noise during the off-cycle; especially if the blower shuts off with the compressor. Check the screw holding the solenoid coil on the reversing valve for tightness.

Oscar

In his spare time, Oscar loves tinkering with electronics. Solar panels, wiring, old TVs and sometimes DIY powerwalls. When he is not busy trying not to electrocute himself, you can find him in the garden tending to his vegetables and chickens.

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