Dometic RV Air Conditioner Not Blowing Cold Air – What to Do?

Rooftop air conditioners are used in many motorhomes, fifth-wheel campers, and large travel trailers. When the RV air conditioner not cooling, it means you have something that goes wrong with your device.

One of the most common is the AC stops blowing cold air, and either your vacation or worse, if you are a full-time RVer, the temperatures can rise.

If you have noticed your RV‘s air conditioner isn’t blowing cold air like it used to, or the temperatures are getting warmer by a few degrees, there are some things you can do.

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Before you call a professional, it is worth checking some of the components of your AC to make sure it isn’t something simple. (Learn How to Clean Underside of Camper Awning)

In our guide, you can learn how an RV air conditioner works and what you need to check as part of your Dometic RV air conditioner troubleshooting to find out why it’s not working.

By the end, you’ll have a much better understanding of what to do after you conclude your Dometic duo therm air conditioner troubleshooting and why your RV air conditioner can’t keep you cold.

How Do I Reset My Dometic RV Air Conditioner?

One of the key things you can go through is resetting your RV air conditioner. It could be nothing more than the settings that stop your RV AC unit from cooling. Here are the steps to reset your Dometic RV Air conditioner.

  1. Press the “+” or “―” button to change the temperature set-point. You will see the temperature set-point displayed as two digits on the LCD screen.
  2. Press the “+” button to increase and the “―” to decrease the temperature setpoint. You can discover, the maximum set-point for your system is 90º F, and the active operating mode will determine the minimum set-point.

Heating has a minimum of 40º Fahrenheit, and the minimum you can set for cooling is 55º F.

“Off” – Off Mode

When selected, the LCD will be blank, and the Off green LED will turn on for 15 seconds, then it will turn off.

“Cool” – Cool Mode

The system cycles the compressor On and Off according to the room air temperature and the temperature set-point shown on the Single Zone LCD thermostat in Cool air mode.

The fan turns on first and is followed by the compressor after around 2 -minutes. Here, you can find 3 fan speed selections:

Lo – (LOW): Your fan operates at low speed as the compressor cycles ON and OFF.

Hi – (HIGH): The blower motor and fan operates at high speed as the compressor cycles ON and OFF.

Au – (AUTO): When the auto fan is selected, the fan speed varies based on any difference between the temperature set-point and the room air temperature. In this auto fan mode, the compressor and fan cycle On and Off using the thermostat.

Why is My AC Running But Not Cooling?

You can have simple issues like the thermostat set incorrectly or a dirty filter. It could lead to something more drastic such as needing to replace components. Here are the key things that stop your AC from cooling as it should. (Learn How to Prepare For Full Time RV Living)


Incorrect Set Thermostat

Check your thermostat settings and make sure it’s set to cool and not to blow hot air. If your thermostat is set to cool, check the temperature and see if it has been changed.

If it has been turned off or set for a constant fan, switch it back to the cooling operation. Once your system kicks in, wait a few minutes, and check you have cold air blowing rather than warm air. If it’s cold, you have resolved the problem.

If your air conditioner not blowing cold air now, carry on with the following fixes or check the relay board.

Dirty Air Filters

Your RV AC unit could include air filters situated in or around your indoor air handler unit. It is the filter’s job to catch dirt and other airborne particles before entering the air handler unit. Doing this keeps the components of the system working and staying clean.

A dirty air filter can block cool air airflow and reduce cooling, or it could lead to your AC system shutting down. You can clean your filer weekly with soap and water to fix this issue.

Condenser Unit is Blocked

Your air conditioning system has outdoor condenser coils. The exterior of your condenser unit will have a large coil that wraps around the outside of the unit. The coil includes the thin metal “fins” that help cool the unit. If your RV air conditioner is running but not cooling, you could have a blocked or clogged condenser coil. (Read Refrigerators For Campers)

When correctly working, the condenser fan draws air into the unit through the condenser coil and pulls heat from your RV.

Damaged Heat Pumps

In some cases, an outdoor unit could include a heat pump. These appear to be like an AC unit but with different components to let them cool and heat your home.

In cooling operation, they work like an AC’s condenser unit and are subject to the same issues such as dirty, clogged coils, frozen, or refrigerant leaks, among others. (Learn How To Paint RV Exterior Fiberglass)

If your heat pump system doesn’t cool, check the thermostat, air filter, and condenser unit for the above. If all these are okay, you may need an AC specialist to repair your RV AC.

Frozen Evaporator Coil

The indoor side of your central air conditioning system includes an evaporator coil. Warm indoor air will pass through the evaporator coil as heat and humidity are removed from the air. Cooler air is then circulated back to your RV.

Refrigerant Leaks

Refrigerant is vital for the cooling process as it changes from a liquid to a gas and draws heat energy and humidity from indoor your RV’s air and pushes it outside.

The extent of a refrigerant leak could contribute to an AC system not blowing cold air. Your system may run for longer periods of time without adequately cooling your home, or it can cause a damaged or failed compressor and complete system shutdown. (Learn How To Run RV Refrigerator Operation While Driving)

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How Do You Reset an RV Air Conditioner?

You often find there aren’t many differences between air conditioner brands for how they are configured for various RV models.

One of the more common is Dometic Air Conditioners. To troubleshoot your AC problems requires some mechanical and electrical knowledge and your AC owners’ manual and thermostat owners’ manual.

Make sure your AC circuit breakers are not tripped? If they have, you can reset these by turning them off and then putting them back on. If your air conditioner not blowing cold air after this, check the following.

Next, remove the AC cover for the filter. Turn on your air conditioner and see if you can smell or see anything that isn’t normal. Check the thermostat, carefully remove the thermostat from the wall, and see if it is possible to disconnect the cable.

One area it could be is the capacitor. Remember capacitors keep charge in them when mains power is turned off.

  1. Make sure the power is off to the device.
  2. Follow the wires and note which one goes where.
  3. Drain any lingering charge from the old capacitor. The way to do this is to wear insulated gloves and connect both ends of the terminals with a screwdriver.
  4. Remove the capacitor and insert a new one.
  5. Turn on your power and try to turn the RV’s rooftop air conditioner back on.

How Do I Know If My RV AC is Low on Freon?

There are a few signs your AC can be losing refrigerant.

  1. It takes ages for your RV to cool off.
  2. Vents don’t blow cool air.
  3. Your rooftop AC can’t reach the set temperature.
  4. You can see ice on refrigerant lines.
  5. Water leaks around your heater.

Another thing to know is the refrigerant an air conditioner uses. AC’s a few years old use R-22 or Freon, although modern air conditioners use the R-438A refrigerant.

You will find RVs have two main parts, the sealed refrigeration system and the air handling system.

Most RVs on R-22 systems are typically sealed units and come without charging ports. The ban on R-22 refrigerant began in 2010. Any leaks of this nature need a professional and you may need parts replaced.

Leaks can be in the form of a small hole and affect the flow of cold air. Leaks in AC intake components and exhaust lead to all sorts of issues in your trailer.

Wires poking from the RV air conditioner intake duct of your trailer can cause this. Seal them up with foil tape so hot air can’t leak into the intake.

If seals between the exhaust ducts and rooftop air conditioner wear, cool air can blow through the ducts and in your trailer roof rather than into your RV.

Dirty in your compressor can prevent normal operation. Your RV’s maintenance schedule should include cleaning any areas around the compressor. If your RV is parked up, cover the rooftop AC unit. (Find the Best Portable Air Conditioners For RV)

Hot weather can be one reason your air conditioner not blowing cold air. Many RVs don’t have particularly good insulation, and if your RV is directly under the sun in hot weather. Interior heat can be far more than what your AC can push out.

Dometic RV Air Conditioner Not Blowing Cold Air - What to Do (2)

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