Dometic RV Air Conditioner Troubleshooting: Common Problems and Solutions

Dometic RV Air Conditioner Troubleshooting

When you are in your RV driving down the road, you want to experience the cool air coming from the vents to flow throughout your vehicle, especially during those warm days and nights.

Now, imagine trying to turn on your AC and then nothing comes out, or perhaps it works but only for a short while.

However, even if it works, instead of releasing cool air, it releases hotter air which only makes the matter worse.

You decide to roll down your window so you can generate a little breeze as you drive, but this is not how it?s supposed to be.

Furthermore, driving at night with an open window is not safe at all, especially when you are in the middle of nowhere.

You know that you have to pull over soon and have your air conditioning issue addressed by a professional.

But wait, do you really have to wait for a professional?

Besides, it might be a while before you get hold of a professional.

These tips for Dometic RV air conditioner troubleshooting will help you get many issues under control.

After all, it's always good to know how to DIY!

Dometic RV AC Troubleshooting: Tools you need

Besides having a good electrical and mechanical aptitude as well as a working knowledge of electronics, the following are the basic tools that you need to have:

How does an RV air conditioner work?

In order to diagnose your Dometic air conditioner, it's useful to understand how ACs work.

A typical AC consists of a compressor that circulates cooling fluid through a condenser, and a fan that blows cooled air into your RV.

That's just the few main parts of an AC that actually makes it function accordingly.

A thermostat is responsible for turning off the compressor and the fan. The thermostat is a switch that is attached to the thermometer, and it is kick-started by a single capacitor or more capacitors.

Below is a short video of how AC works:

The 12-volt electrical system of the RV is the one responsible for running the thermostat as well as other controls.

Important Safety Tip

Keep in mind that you will be operating on live circuits and moving parts that are located on the roof of your RV. So, make sure that your fingers do not come close to the moving parts.

If at any point you feel that you will not be able to proceed any further, it's best to backtrack, reassemble anything you may have taken apart, and let a professional handle the rest.

Common Dometic RV Air Conditioner Problems

RV AC is Overheating

Your AC is likely to overheat if you fail to clean the coils. The coils here refer to the tube that extends out from the AC unit.

It is just inevitable, that after a while, these coils will have deposits of pollutants and dirt inside them as a result of their exposure to outdoor conditions.

The dirt and pollutants act as insulators which prevent the refrigerants from absorbing the heat from the inside and then releasing the heat out.

Aside from dirty coils, overheating may be caused by dirt in the filter, an old compressor, short circuit, high voltage, a big room or simply the lack of maintenance.

RV air conditioner is dripping

One of the causes of this problem is the water that has condensed in the wrong place. One of the wrong places where water can condense at times is in the pan located under the air conditioner.

This can happen if the fan does not evaporate the water. Nevertheless, such a buildup of water may be caused by dirty coils, which means that for you to remedy the problem, you simply clean the coils.

A noisy motor

In case your motor is noisy, investigate the issue by removing the cover from the AC and then check to see if everything is in the right place.

Sometimes, the noise may be as a result of the rubber shock absorbers located on the compressor interfering with the unit?s motion.

How to maintain your Dometic RV air conditioner

Open the roof vent once in a while

In case you are spending much of your time engaging in outdoor activities, you definitely do not need the AC to keep running while you are outside, do you?

So, be sure to open up the roof vent so that the moisture can evaporate. This is a simple trick that will keep your AC functioning properly for a long time.

Check the condenser

At least twice a year, check your condenser. You may be having a condenser coil which is blocked by either leaves or dirt.

If the condenser is blocked; the inside of your RV will likely remain hot. To get that cool breezy air in your RV, make sure that you keep checking the condition of your condenser even if just twice a year.

If the condenser is still not cooling even after unblocking it, you may need to look for another one to replace it.

Manage the thermostat settings

You need to have air conditioners in your RV so the air inside it may be cool. However, make sure that you are not overloading the capacity of your RV. 

Instead of setting your AC at a low temperature, simply turn the fan to ?on'. If you do this, your AC will be able to get the heat or cold that you desire in your RV.

Always keep the temperature settings at a moderate level so that your AC unit may have a longer life besides performing better.

Oil the fan

The fan inside the AC unit does a difficult job of keeping the air circulating, so why not ensure that it is in perfect condition?

In order to ensure that it works well as well as for longer, keep it well oiled. In addition to oiling the bearings of the fan, it is a good idea to clean the accumulated debris that is both on the front as well as the rear fan blades.

To fully access both ends of these bearings, you may have to loosen the fan motor from its mounting. In case the RV fan motor has oil tubes for lubricating the fan, simply put a few drops of the machine oil into the tubes located on either end of the motor.

If instead of having ball bearings, the motor has sleeves, dribble just a little amount of oil where the sleeves come into contact with the fan motor shafts.

For these types of motor fans, a small amount of oil can work wonders.

Keep the AC unit covered during offseason

When not using your RV, make sure that your RV air conditioner stays covered. This can help you avoid the repairs which can turn out to be costly. Purchase a cover that is inexpensive to cover your RV whenever the RV is not in use.

Besides, there is a high chance that you are not going to use your RV throughout the year; there will come a time when you will need to store the vehicle for some time.

Whether you decide to store it in some storage facility or just in your driveway, it is always a wise decision to invest in a cover for your RV. 

Besides keeping air conditioners of your RV in top shape, the cover will also protect your RV from the adverse effects of Mother Nature.

Speak to a mechanic

You can use the chat box in the sidebar or the bottom right to speak to a mechanic right now.

Advanced Electrical Maintenance If It's Still Not Cooling

In case the steps above did not solve the issue, check the following one-by-one.

Please bear in mind that this is now advanced maintenance involving working with electricity, so if you're not comfortable, DO NOT proceed and show a professional instead.

Thermostat - Is your thermostat on? Is it set on a much lower temperature compared to the temperature inside your RV?

AC circuit - Have the breakers of your AC circuit tripped? If they have, you need to simply turn them off fully and then turn them back on. Remove the breaker, then using your voltmeter; check the breaker's power supply. If the power supply is available, reset the breaker after reinserting it.

AC cover - Take out the AC cover at the position where the filter usually sits. Then, turn on the AC, do you see or smell anything out of the ordinary such as burned wires or obstructions?

The wires - Look out for broken or loose wires. Here, you can see either one or more RJ11 cables and connectors which look like phone cables. Disconnect these wires and then reconnect them and ensure that they all are seated well.

If you find more than one cable, disconnect and reconnect one cable at a tie and make sure that you connect them properly.

RJ11 connection - Using an eraser, clear up the RJ11 connection?s male end and then with the utmost care, plug and unplug these connections a few times.

Thermostat - Go back to the thermostat and with utmost care, separate the thermostat from the wall and then check whether you are able to disconnect and then reconnect the cable.

If possible, reset the thermostat. You can check your owner?s manual for the proper steps of resetting the thermostat, as the steps are a little different 

More steps to take

If the problem persists even after doing the above, then you need to go outside and carry out further tests.

Precisely, you need to get on your RV's roof to do this. Remember, if you are uncomfortable working with electricity or working on the roof, then let a professional handle it.

  1. Get on the roof and take off the AC shroud so you can access the electrical elements and panels to the motor.
  2. Then, if you have power, use your voltmeter to check the power and then, ensure that the voltage/amperage readings are okay. Check your owner?s manual for guidance.
  3. In case you do not see the proper voltage or amperage, then you have to check for continuity. If continuity is lost, then you need to check the wires for corroded, loose, or broken connections
  4. If the wires are not intact, you might have to redo the connections after opening them. Additionally, you may have no choice but to trace the circuits all the way to the breakers.

Check the control board

Have a look at the control board. Then, follow out any of the connections either out or into the control board.

Does the control board look broken, loose or burnt? Does any component look scorched or discolored? Can you smell burnt insulation?

If there is any wire which is broken or loose, you'll need to replace it.  

If there is anything unusual about the control board, then you may have to replace the control board or you can have it repaired at the nearest RV repair facility.

In addition, make sure you have a look at the thermistor and see if it operates properly.

Connect the thermistor lead to your volt-ohm meter and then apply heat to the copper wire. In case of a drop in resistance, the thermistor is in good condition.

In case your AC is still not functioning properly, you'll need to check whether the capacitors and the relays are operating properly.

Related Content: Ways to Improve Your RV Air Quality, do you really need to?


Your AC is an important component of your RV; however, it cannot work on its own forever.

There are several issues to do with your AC which can be fixed by simply cleaning it regularly and maintaining it. 

For instance, if you stick to a cleaning schedule every six months, you will be able to avoid many of the issues mentioned above.

Hopefully, the above information will teach you some Dometic RV air conditioner troubleshooting techniques whenever you need to do so. 

Remember that even though you can do all of the above by yourself, in case the problem is not fixed; you should involve the services of a professional.

Having said that, remember to never service a running AC unit or one which is still plugged in.

Related Review: Dehumidifier for RV, get rid of damp air easily!

12 thoughts on “Dometic RV Air Conditioner Troubleshooting: Common Problems and Solutions”

  1. The rooftop air conditioners used on motor homes are made in such a way to provide many years of dependable use. Especially if you maintain them. These repair and maintenance tips are very simple to follow, even for those without much hands-on experience. Thanks for sharing these great tips.

  2. I live on a boat, I went on vacation, turned it off I come back and now it’s not working, maybe the compressor? It’s only two years old, what should I do?

  3. I found it interesting that you state that it’s important to have AC when you’re driving in the heat. My brother and his wife want to buy an RV and cruise the country. I will send them this information so they can make sure to get a good AC unit for their trips.

  4. My a/c worked but after a move .It now dont work . I blows cool air and has a smell. Crazy a 90 mile trip caused not AC . Any tips would be grateful.

  5. AC runs and blows cool air. After running for several minutes the blower will shut down and compressor will continue to run, then a few seconds later the blower comes back on. This continues until cooling tempature is reached. Is this common?

  6. I bought a new trailer with a 135000 btu ac. It would come on for two mins and go off for two min. Looking at the papers that came with trailer I saw there was a duct divider that needed slots made in it.i removed divider and put the amount of slots needed for the height of unit. Problems solved! I’ve searched for this problem on internet with no one offering this as a solution. Please post this for me as I dont know how to.

    I picked up my Dads motorhome after he had a new Dometic roof
    top unit installed. I can hear the compressor
    come on but it blows hot air. Could the crooked
    man that installed it have hooked the compressor
    backwards. It gets hotter when the compressor
    comes on.


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