What Causes an RV AC to Freeze Up and How to Fix It
The warmer months are here, and that means more time spent out in your RV. It also means you’re probably going to be using your RV air conditioner to keep cool. Unfortunately, this time of year is when a lot of people notice their RV AC freezing up.
Sometimes this is a one-time event caused by an excess of humidity in the air and doesn’t require any repairs at all. However, if it happens over and over again, there’s likely a reason behind the freeze-ups, and you will definitely want to get to the bottom of it and fix the problem.
Luckily, most of these fixes are fairly straightforward and inexpensive. The list below includes all of the things we recommend doing to stop your RV AC freezing up issues. Use these so you can fully enjoy the spring and summer in your travel trailer or motorhome.
How to defrost an RV AC
Before we jump into the various potential causes and their fixes, let’s talk about how to defrost a frozen RV AC unit. This is a super easy process, but it can get a little bit messy, so be prepared to do some cleanup.
First, remove the plastic AC cover found on the inside of the RV. (Don’t lose any of the screws!) Once the cover is removed, turn on the fan of your AC unit, but make sure the cooling feature is turned off. This will pull warm air through the unit, melting any ice that has built up.
Of course, melted ice is water, and that water will need to go somewhere—and this is where the mess comes in. Ideally, all that water would be caught by the AC drip pan. However, it’s usually so much that it just can’t handle it all. In this case, it ends up making its way into the RV and onto the floor below. We recommend placing a bucket under the unit while running the fan in order to catch the falling water.
When you feel confident that the unit has been completely defrosted, let it sit for several hours to dry.
Too much humidity
As mentioned before, one reason for RV AC freezing up issues is simply too much humidity in the air. If your unit freezes up once and never again, this was likely the cause.
If it freezes up every time you visit a humid place, you might consider the possibility that one of the other causes below is working in conjunction with this extra moisture to cause a problem. Running a dehumidifier in the RV can help with this. However, you will also want to look into other possible causes just to be safe.
Dirty air filter
Air conditioners need airflow to function properly. Low airflow will cause RV AC freezing up problems. One of the most common reasons for low airflow is a dirty air filter. These filters should be cleaned regularly—as often as every two weeks if the AC is being run daily—but many RV owners fail to do this bit of maintenance.
Fortunately, this is an incredibly easy fix, as it only requires a quick filter cleaning and replacement.
The next thing to check would be the condenser and evaporator coils. If these are dirty, heat can’t escape properly. This means the unit has to work extra hard to put out cool air. Something that will eventually lead to problems with the RV AC freezing up.
Good news! A brief cleaning should solve the problem.
To clean your condenser and evaporator coils, you will need a screwdriver, a shop vac, a spray bottle full of soapy water, and a soft brush.
Start by unplugging the RV, turning off the generator, and disconnecting the batteries to ensure that no power can get to the AC unit. Once this is done, you can remove the shroud over your AC unit by removing the screws and pulling up on the cover.
With this done, you should be able to see the condenser coils at the back of the unit, as well as the metal housing that contains the evaporator coils. Find the screws holding the housing in place, remove them, and carefully remove the housing. Make sure not to damage the gasket or cut your hands.
Now all coils should be exposed and you can start the cleaning process. Begin by using your shop vac to very carefully vacuum away as much dirt and dust as possible. The soft brush attachment can be very useful during this step.
Finally, use your soapy water in a spray bottle to get the coils nice and wet, as well as remove any dirt that might be lodged in the crevices. Let the water sit for a few minutes before gently wiping the coils down with a cloth.
Inspect the coils for any bent fins and straighten them out using a knife or fin comb. Once your fins are all straight, let the unit dry completely and then replace the metal housing and shroud.
Bad flow divider
Another cause of RV AC freezing up problems? A bad flow divider. This is the divider between the hot air intake and the cold air output. The divider can move around while driving. This leaves a poor seal and allowing air to seep from one side to the other. As a result, the AC unit thinks the air it is putting out isn’t cold enough, leading it to work harder and eventually freeze.
To fix this issue, you will need to reposition the flow divider and create a seal. Hold the divider in place using HVAC foil tape. This video is a great example of this quick and easy fix.
So far, every problem we’ve listed has been super easy to take care of with no new parts. If none of these fixes the problem and your AC unit is connected to a wall-mounted thermostat, the next thing to check is that thermostat. Unfortunately, if your problem is a broken thermostat, you’re looking at a slightly more difficult and more expensive job.
First, you will need to check if your thermostat is bad. To do this, check the temperature of your rig using a thermometer and compare it to the temperature reading on the thermostat. If they match or are very close, the thermostat is likely not your problem. If you get a different reading, you are probably onto something.
This particular job is harder than the jobs listed above. However, it isn’t incredibly difficult if you have experience with minor electrical work. This video shows you how to do the job. If you don’t have experience with this, hiring an RV tech might be a better option.
The final thing that could cause RV AC freezing up issues is low refrigerant. This is actually highly unlikely because RV air conditioners are factory sealed, meaning no refrigerant should get out. However, it is possible to develop a leak.
If you do find that leaking has occurred and that it’s the source of your problem, you will be looking at buying a new unit in order to fix the issue. This is because these closed-loop systems don’t allow for more refrigerant to be added. Once it’s gone it’s gone, and the AC is no longer useful.
Track your RV maintenance
Make sure you keep track of all your RV maintenance and repairs with an online tool such as RV LIFE Maintenance. Not only can you keep all of your documents in one place, but you’ll also receive timely reminders when maintenance is due to help you avoid costly repairs and potentially serious accidents.