Air conditioners freeze up from time to time whether it’s because of basic neglect or the fact that the system is just getting old and needs a touch of tender loving care. If it freezes up in your RV, however, that’s a whole new can of worms because the odds are, it’ll happen when you’re as far away from professional help as possible.

The first thing to do is avoid panicking over the situation, even if it happens in the middle of the summer. When an A/C freezes up, it’s often an indication that the evaporator coils are dirty. The second thing that you do is shut it all off and then start troubleshooting.

If you don’t have any HVAC experience, you’re better off starting with what you know and working your way out from there. Although the evaporator coils are a very common culprit when A/Cs freeze up, there may not be a problem at all and there are several things that can jumpstart an RV A/C freezing up.

Here’s a small list of the more common issues:

  • Dirty evaporator coils
  • Low refrigerant
  • Faulty thermostat
  • An obstruction somewhere
  • Dirty condenser
  • Dirty air filter
  • Bad freeze sensor
  • Bad capacitor

But before you get started on troubleshooting the problem, you should go ahead and start defrosting your RV’s air condition.

Start by defrosting your A/C

Road of Waterdrops
Photo by Tamas Kolossa / Unsplash

Before you can do anything with the A/C, you have to defrost it. Since it’s frozen up at this point, it will be difficult to run through certain checks until the A/C can function again, even if it is just a temporary run before it freezes back up again.

Before you begin the defrosting process, collect some towels because things are about to get seriously wet. You can use the towels to catch most of the dripping as the unit thaws.

Here’s how to defrost your RV’s air condition:

  • Locate your A/C unit (usually inside of the RV or occasionally in a separate compartment)
  • Keep your A/C running but on fan only, since you obviously don’t want to keep the A/C running
  • Keep running the fan for as long as it takes until all of the frost is clear and everything that you touch is room temperature

If you don’t defrost the system first, there are certain functions that will be inaccessible or aspects of your A/C that are not observable unless you have a room temperature unit

Troubleshooting your RV’s Air Conditioning

Vintage RV on road trip
Photo by Steven Weeks / Unsplash

Now that the frost is cleared up, you can start troubleshooting the system until your heart’s content or until you have to call in an HVAC specialist. If you turn the cooling function back on and you get cold air coming out of the vents, that points to the evaporator coils or the condenser.

That’s not what it always means but it’s a step in the right direction. Let’s go through each of the possible problems one by one.

Evaporator coils

Dirty evaporator coils should always be at the top of your troubleshooting list because it is the most common issue that causes your system to freeze up. It’s something that you should perform preventative maintenance on with some regularity.

The problem is that most people don’t go about their busy lives, stopping occasionally to think to themselves, “I really should go out to the RV and clean those evaporator coils today.” It is what it is. Fortunately, it only takes one freeze-up to disillusion you of ever neglecting the evaporator coils again.

So, when the A/C goes south, it’s time to grab a few things, access your RV air conditioner and get to cleaning:

  • You’ll need a good vacuum with a hose (such as a shop-vac)
  • An old toothbrush and a rag
  • Mild soap, like Dial or Dawn dish soap
  • Screwdriver (Phillips and flat)
  • An empty bottle with a light amount of soap, filled to the top with water

Coils are pretty easy to clean. You just need to make sure that you vacuum all of the loose junk off of them first, before you start scrubbing. If you start scrubbing with your soap and water, all of that loose debris will turn into rolled-up globs of filth that will fall back down into the unit.

Scrub those coils until they look as close as possible to the original version. Don’t leave anything to chance. Get underneath them, around them, the sides, everything. When you’re all done, reassemble your unit and attempt to run the A/C on cool.

Bad capacitor, freeze sensor, or thermostat

You may or may not have a thermostat control and you may or may not have a freeze sensor. When most people purchase an RV, they’re far more enamored with the flip-down bunk beds and the smart microwave than they are over whether or not the RV is equipped with a freeze sensor.

You’ll know you have a for-real thermostat if you can control more than A/C – On/Off and Fan. If you’re constantly turning down the thermostat to keep the A/C in pace with the temperature, you have a bad thermostat.

You can double-check this by bringing an outside thermometer into the RV to compare the real temperature to what your thermostat is saying. If you have a freeze sensor, you would come across it while cleaning your evaporator coils, as that is where it is typically installed.

The freezer unit is responsible for detecting frost build-up and getting rid of it. If it is no longer functional, that’s going to be a problem.

Lastly, within this group of components that you may or may not have, is the capacitor, which is the one component in this group that all RV air conditioners have. The capacitor is what runs the fan, which pulls the cold air out and blows it through the ventilation system in your RV.

If the capacitor has gone on vacation or is no longer functioning at an optimal level, all of that icy air has nowhere to go and will just hang out, freezing up everything around it. In most cases, it’s easy to replace, but some are a little more complicated so you may need it professionally serviced.

Dirty filters or low refrigerant

We lumped these two together because they are part of what should be a routine, preventative maintenance program. It’s important to always check your refrigerant and either keep your filter(s) clean or replace them regularly.

A dirty air filter can wreak havoc on your HVAC system throughout the RV, as well as your electrical system on top of freezing up your A/C. Both the air filter and the refrigerant level hold an enormous amount of power over the functionality of your A/C.

Be sure to check your refrigerant levels frequently and clean your air filter. If you have a “one-time” use filter, be sure to change it at the intervals recommended by the manufacturer.  Fortunately, air filters for your RV air conditioner are easy to replace and cheap.


You would be surprised at how many animals out there would love to set up their home and raise a family inside your air conditioner. Birds and other nesting animals will find a way to get in there and then they will fill the spaces in your unit up with all of their trash.

It’s kind of like the roommate that you took on despite your misgivings, only to find that your misgivings were completely appropriate. It’s not something that you need to check over as frequently as your air filters and refrigerant levels, but it is certainly something that you should check over before you hit the road on your next RV adventure.

It doesn’t have to be animals either. When you pull into campgrounds, odds are that you scrape through low-hanging trees all of the time. It’s only a matter of time before twigs that snag on your unit build up to a certain level.

It doesn’t take much before the build-up becomes enough of an obstruction to start causing a lot of issues with your unit.

Volatile temperatures

In some areas of the world, there’s really no such thing as an average, everyday temperature directly associated with the season at hand. It may be 85°F during the day, only to drop down to 57°F at night time.

Most RV air conditioners are designed to handle external temperatures that are above 65°F, however, once it drops below that outside, and the inside temperature is higher, your A/C unit will start to struggle.

The problem is that the A/C unit is struggling very hard to cool air that is already cool, which can eventually cause your unit to freeze up if it continues unabated. If you need to stay cool inside, pay attention to the outside and crank down some of those windows when the outside air is plenty cool enough to do the work the A/C can’t.

Final thoughts

It’s a pain when the A/C goes out, especially when it is freezing up and you’re not sure why because you have to have the patience to allow it to thaw. In the meantime, it may be 95° outside and you’re dying to get it going again.

As mentioned above, preventative maintenance is so important that you can’t afford to let it fall to the wayside. Stay on top of your A/C. It goes without saying that if you take care of your A/C, it will take care of you.