What to Do If Your Dometic RV Air Conditioner Is Not Cooling

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Keeping cool, especially in the summer, is the fine line RV owners walk between a comfortable ride and a sweaty nightmare. When you turn your AC on, you expect it to do one thing: cool down the RV. If you’ve done regular maintenance on your unit, you shouldn’t have much to worry about. 

When the temperature climbs and you reach for the thermostat of your Dometic air conditioner and don’t feel any cold air, you’re in trouble. Dometic brand air conditioner units are meant to be long lasting and reliable. If your Dometic RV AC isn’t blowing cold air, you’ll be looking for the reason, and for a fix. 

The first thing you should verify when your Dometic AC isn’t blowing cold air is the power panel. Sometimes, the source of your problem is something small and simple like a blown fuse. If you have a voltmeter, you can run a secondary check to make sure it’s correctly powered. 

Dometic RV Air Conditioner Not Cooling 

As reliable as these models are, Dometic AC units on RVs can encounter snags and hiccups just like everything else. There are a couple of things that could be making it that your air conditioner is not cooling. 

If you’re not sure what is causing the problem, you can always call a specialist from Dometic. They’ll be able to take the time needed to analyze your entire unit and systems to find the real cause. They’ll also have the tools and expertise to fix it. 

Replacing or repairing a single part might not be too expensive, but replacing the whole unit is another story. Since replacing an RV air conditioner can be so pricey, it’s best to handle yours with the best possible care. 

Blown Or Switched Fuses 

Sometimes the small things can cause bigger issues. For example, a fuse that is blown or tripped could be the cause. This keeps the air conditioner unit from receiving the power it needs to properly cool. 

Thankfully, smaller problems also have simpler solutions. Once you check the power panel and confirm that a fuse is the culprit, you either need to reset or replace it. Replacing a fuse isn’t a difficult task, and replacement fuses can be found inexpensively at hardware stores or online. 

Once you’ve got that installed, try your AC again. Put your hand near it to see if you immediately feel cold air flowing out. If you do, take a few steps back to see if it’s cooling the space adequately. If you can feel cold air reaching as far as it normally would under regular conditions, then your AC should be in working order again. 

Shortage Of Power 

Did you just upgrade your older Dometic AC unit to a new one? Newer units have all of the bells and whistles of the modern age, but that luxury comes at a price. 

When you upgrade to smart thermostats, or even just more robust models, the AC needs more power. However, your RV might not be able to supply as much as is needed, especially with other household appliances connected

Even shore power at some older campsites might fall short of what is needed to keep newer Dometic models running sharply. Instead of heading to a new campground with a higher charge, you can instead turn something off. 

Consider electrical devices in the RV that you can unhook and shut down while you wait for the AC to cool your vehicle. Things you might not need right at that moment, like a microwave, coffee maker, or even the TV can help the power load. 

The Unit Needs To Be Reset

Another key thing you can do to keep the unit running in good shape is reset it. Dometic units have a few distinct settings, and your configuration of these settings could be why your unit isn’t cooling. 

Find the plus and minus buttons on your unit that change the temperature set-point. Most newer models will have the temperature set on an LCD screen. You increase or decrease the temperature set-point using these buttons. 

Press and hold the plus button while also pressing the on/off mode button for three seconds. The LCD will show “– –” indicating that it is reset. 

Usually, this could solve the issues you’re having with your Dometic RV air conditioner unit not cooling. The thermostat getting thrown off will often lead to trouble with the unit, so be sure to try resetting it first.

Refrigerant Leak 

One of the vital parts of the cooling process is refrigerant. It changes from a liquid to a gas, drawing heat energy and humidity from inside the RV. It then takes that energy and pushes it outside, making the air cooler. 

Refrigerant leaks aren’t only troublesome when you want to cool down the RV, they can also be dangerous. If your unit runs without refrigerant, it might run for quite a while without actually doing anything. This wastes electricity and can damage the compressor. 

How Can I Tell My RV AC Is Low On Freon? 

Freon leaking from your Dometic AC unit can show a few signs, thankfully, making it easier to diagnose. Aside from the problem you’re having, wherein the AC takes too long to cool the vehicle, some of those signs include: 

  1. The vents aren’t blowing any cool air. 
  2. The unit on your AC roof can’t reach the temperature set on your thermostat. 
  3. You see ice or frost accumulating on the refrigerant lines. 
  4. Your heater is leaking water. 

Leaks will usually appear from small cracks or holes. This will, of course, impact the flow of nice, cooling air. Usually, leaks might be caused by wires poking out from the intake duct. 

Refrigerants are also toxic, and the fumes could be hazardous to the health of both humans and animals. Check all of your refrigerant tubes and valves to be sure there aren’t any leaks, wearing a mask and gloves for your protection. 

If you find a refrigerant leak, use a silicone sealant to block up where it is escaping. This should hold you until you can replace the tubes. You shouldn’t consider it a permanent solution. 

Dirty Air Filter

One of the common headaches of AC units in both homes and RVs is the maintenance needed on the air filters. They are what keeps debris, lint, and other particulates from entering or exiting the unit. 

If the filter is dirty or dusty, the debris is keeping enough cold air from escaping to chill a room. If it’s extremely gnarly, then the compressor could be choked of proper airflow. 

Clean out the filter as needed. The Dometic brochure suggests doing so every two weeks when it is in frequent use. All you need to do to clean it is run it under some warm water with a splash of soap. Let it dry completely and stick it back into place. 

Do not run the unit without the filter in place, as this could cause dirt and detritus to clog the evaporator coil. If your evaporator coil gets clogged, you’ll be right back where you started: an air conditioner that won’t cool. 

Damaged Heat Pump

In outdoor units, there could be heat pumps that let them cool or heat your vehicle. They act as a condenser for a Dometic AC, and should be kept clean. Check out the heat pumps to see if they look damaged or dirty. If you can’t clear the dirt or repair the damage, you might need to have it replaced. 

RV AC Blows Cold Then Warm 

If you test out your AC and find that it pumps out cold air for a few minutes before switching to warm air, it could be an issue with the capacitor. Older air conditioners will run into this problem more readily, whereas newer units are less prone to it. Still, that doesn’t mean they’re infallible, and it’s worth checking the capacitor anyway. 

Take a good look at your capacitor and see if it is defective or broken. The usual way you’ll test this is through a resistance test. 

Your Dometic RV air conditioner has two capacitors, as is customary in all RV air conditioners. The two types of capacitors it has are referred to as ‘motor run’ and ‘motor start. Motor run capacitors are used in the blower fan circuit, and the motor start is in the compressor. 

Running a resistance or capacitance check will operate on both of these, so there’s no need to double check them individually. 

A capacitance test will give you the best look at the capacitors specifications, and help you see what is in the ‘normal’ range. 

How To Test Your Dometic AC Capacitor 

  1. Switch off the AC circuit breaker to the RV, or disconnect from shore power if you’re currently hooked up to it. When locating your AC circuit breaker, it will usually be in the electrical load center. 
  2. On your RV’s roof, remove the housing that covers your Dometic RV AC unit, also called the shroud. This is a fairly simple task; you’ll only need a screwdriver with the correct head to get it done. 
    1. If you have the time, now would be a good opportunity to clean the shroud as well. While its job is to protect your AC from dirt and debris, it collects a lot of it itself. Once it wears down, your AC is susceptible to wear and tear that will inhibit its ability to blow cold air. 
  3. The capacitors will be inside an enclosure on the unit that further protects them. Inspect the enclosures and take a look at the capacitors. 
  4. Locate the electrical terminals on top of the capacitors themselves. You’ll be discharging these by shorting them out. 

After the discharge, place the red (positive) lead or your multimeter on a positive terminal on the capacitor. Then, apply the black (negative) lead on the corresponding terminal. Make sure the multimeter is in capacitor mode. 

  1. See what the appropriate capacitance value on your capacitor should be. If the reading on the multimeter doesn’t match that, your capacitor is to blame for the issue. 
  2. Repeat these steps or both capacitors. If you see a mismatched reading from the start, though, you might not need to test the second one. 

If your capacitor is not reading correctly, you will have to replace the capacitor. This is something you should contact a professional to do, unless you are extremely versed in RV HVAC repair. Dometic might be able to send a specialist to you directly to have the issue addressed. 

It’s also entirely possible that the reason your capacitor is not working is, once again, the fuses. The two fuses on the units disconnect could be faulty. Your Dometic RV AC fan has its own power source, and it’s possible that they’ve gone bad independently. 

Other Troubleshooting Tips 

  • Check the voltage of the compressor with a multimeter or voltmeter. The compressor may be operational, but not getting a strong enough supply of power to cool the room. If the power is normal, a connected multimeter will show 13.4 volts on a Dometic unit. 
  • Another sign of a faulty compressor that doesn’t need a special tool to test is silence and stillness. When the compressor is working well, you’ll be able to hear sounds coming from it and feel the vibrations. If you don’t hear or feel anything, the problem is your compressor. 
  • Are there any tears or holes in the duct system? Holes could be letting air escape, preventing your AC from cooling. If you find a rip in the duct, a solid duct tape will keep it in working order until you can replace it. 
  • Blocked coils can be the reason your Dometic RV air conditioner isn’t cooling. Take an air compressor and blast away dirt and dust. You need these coils to be free from blockages of any kind to ensure your ACs longevity. 
  • Your registers can suffer when they get dirty as well. When they’re blocked, improper airflow will make it harder for the AC to cool things down. 

A big takeaway here is that you should keep your Dometic RV AC and its components clean. Regular upkeep and maintenance will make it so you don’t have to worry as much about your AC not cooling. 


There are a few things that could cause your Dometic RV air conditioner unit to not cool the vehicle properly. Simple things like a blown fuse or the unit needing to be reset can be simple, throwaway fixes that you don’t have to worry too much about. 

Other troubleshooting issues are more harrowing. For example, it can be dangerous and taxing to test your AC’s capacitor. You might also have leaks, clogs, or issues with the filter. 

The best thing to do to keep your Dometic RV AC unit in the best shape possible is to clean it frequently. 

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