RV Air Conditioner Freeze Up – 10 Causes & How To Fix Them

Few things are as uncomfortable as staying in your RV without air conditioning, so finding out how to fix an RV air conditioner freeze up is a top priority if you find yourself in this situation.

With any repair, you first need to understand why the problem is occurring before you can go about fixing it.

We’ll cover the main causes of RV air conditioners freezing up and how to fix them in today’s guide.

Why Do RV Air Conditioners Freeze Up? 10 Main Causes

Here are the most common reasons why RV AC units freeze up:

  1. Dirty Condenser Or Evaporator Coils
  2. The A/C Unit Is Obstructed
  3. Outside Temp Is Too Low
  4. Dirty Air Filter
  5. Bad Thermostat
  6. Bad Flow Divider Or Baffle
  7. High Humidity
  8. Dislodged or Defective Freeze Sensor
  9. Weak Or Bad Capacitor
  10. Low Refrigerant Or Coolant

We’ll go through how to diagnose each of these RV AC problems and how to fix each one below.

Before we do any of these, we first need to defrost the RV AC unit.

How To Defrost Your RV Air Conditioner

We need to defrost the air conditioning unit in your RV before we can diagnose the problem, so let’s cover that process.

Fortunately, it’s a pretty easy one but can take a little time:

  • Step 1: Remove the cover of your A/C unit inside your RV (you’ll probably need a screwdriver or small pry bar depending on the cover)
  • Step 2: Turn the A/C fan on high setting (be sure not to turn the cooling function on, only the fan).
  • Step 3: Put towels and a bucket below the air conditioner to catch drips of water while the unit defrosts.
  • Step 4: Once the unit has defrosted and stopped dripping, let the unit dry out fully.  You can continue running the unit’s fan and you can even aim another small fan at the unit to speed up this process.

Problem 1: Dirty RV A/C Condenser Or Evaporator Coils

The most common reason why RV air conditioners freeze up is due to low airflow, and that’s caused by blockages in the condenser and/or evaporator coils.

Each set of coils has it’s own job: the evaporator coils remove the heat from the air, and the condenser coils move that heat outside.

These coils need to be cleaned regularly and if they aren’t, the coils have to work harder than usual to get the air cool inside your RV.

The dirt and gunk that forms on the coils block these processes from happening easily, and then ice will form on the coils since the system is working harder to cool the air.

How To Clean Your RV’s Evaporator And Condenser Coils

Before You Start: Gather Your Supplies

You’ll need the following items to clean your AC coils on your RV:

Step 1: Locate The RV A/C Unit

Before you can clean anything, you first need to know where your AC unit is!  This is pretty easy, as most RV air conditioners are on the roof.  You should be able to see the condenser coils and evaporator coils once you get the housing off, which you can do with a screwdriver.

Step 2: Power Everything Off

Make sure to unplug your RV from power or turn off any generators and disconnect your batteries.

As a second option, you could just turn off the breaker for your A/C unit and remove the fuse while working on the A/C.

Either way, be certain that there’s no 110V or 12V power going to the air conditioner.

Step 3: Remove The RV Air Conditioner Unit Cover

Remove the screws covering your RV’s A/C unit, and put them somewhere safe so you don’t misplace them.

Most A/C units on RVs will have the evaporator coils in front and the condenser coils in back.

Safety tip: the sheet metal used for the housing can be sharp, so wear safety gloves.  Also, bees and wasps like to make nests in this housing, so be careful when taking it off.

Step 4: Vacuum The Air Conditioner Coils

Using a brush attachment, vacuum off any dirt and debris from the coils.  Be careful not to knock any of it into the openings that lead into the RV.

Step 5: Clean The RV AC Unit Coils

You can mix a solution of soap (like dish soap) and water in a spray bottle and spray down both sets of coils.

Let this solution set on the coils for a few minutes, then wipe them down with a cloth or brush, and vacuum them again to remove any stubborn debris you knocked loose.

Step 6: Rinse And Repeat

Spray the coils off with water and repeat the cleaning process if necessary – some of the debris and film can really get baked on to these coils and you might need to do this more than once.

Step 7: Take A Good Look

Inspect the coils and try to get as much gunk off as you possibly can – again, the better and cleaner the coils are, the better your RV’s A/C unit is going to perform.

Look for any damaged, warped, or bent fins on the coils – if you see a few you can fix them with needle nose pliers, a screwdriver, or small knife.

If you have a lot of fins that are in bad shape you can correct them with a fin comb

Step 8: Put Everything Back Together

While you’ve got everything pulled apart, go ahead and clean the inside and outside of the A/C unit housing with soap and water.

Put everything back together, restore power, and test your RV’s air conditioner to see if this did the trick.

Here’s a great video giving you a visual guide on how to clean off those RV AC coils:

Problem 2: A/C Unit Obstruction

Visually check the AC unit to see if there are any bird nests, animals, or heavy brush or debris physically surrounding the AC unit’s coils on the inside or outside of the housing.

If you’re parked under thick brush and it’s resting on or around the A/C unit, this can cause the RV air conditioner to freeze up due to lack of airflow – same for birds nests and animals.

Problem 3: The Outside Temp Is Too Low

Most RV air conditioners are not made to handle outdoor air temperatures lower than 65 degrees.

If you’re further cooling this already cool air, it can cause your RV AC unit to freeze up.

If you’re camping in temperatures lower than 65 degrees, simply turn the AC unit off and open the windows to keep cool at night.

Problem 4: Dirty RV A/C Unit Air Filter

The issues caused by a dirty or clogged air filter reduce air flow, which is the most common culprit of RV AC freeze ups.

You should be replacing your air filter annually, and cleaning it about once a month during seasons of heavy use.

You can get replacement ones cheaply and they’re quick to install.

How To Clean Your RV Air Conditoner’s Air Filter

This process is extremely simple:

  • Step 1: Wipe any dirt or debris off your air filter
  • Step 2: Wash with soap and water, let dry, and put air filter back
  • Step 3: (Optional): Soak for 10-15 minutes in a 1:8 solution of vinegar and water

Check out this video on how to replace and clean your RV’s AC filter:

Problem 5: Bad Flow Divider Or Baffle

The baffle (or flow divider) in your RV’s air conditioner keeps the hot air coming in to the unit separate from the cold air blowing out of the unit.

If there is a leak between the two supplies, the unit can freeze over because the already cold air is being further cooled by the hot air inlet.

Check the baffle to make sure it’s properly positioned.

Once everything is reseated properly, you can take some HVAC foil tape to seal up any leaks and prevent this from being a future problem.

You can see this process here:

Problem 6: Broken Thermostat

If you’re constantly turning down your thermostat in your RV to keep the A/C working, the thermostat may be broken.

Note that this only applies to RV A/C units that actually have a thermostat control – if yours is strictly on/off and fan settings, you can rule this out.

If you have an older thermostat, it may be wise to change it since older ones are known to have a lot of issues with accurately reading temperatures anyway.

How To Check Your Thermostat Reading:

  • Step 1: Check the temperature inside your RV with a thermometer
  • Step 2: Compare that temperature to the temperature you have your AC set to
  • Step 3: If these numbers aren’t the same, you have a thermostat that’s acting up.

If you are comfortable with minor electrical repairs, you should be fine doing a thermostat replacement.

Check out this video for a walkthrough on how to replace your RV thermostat:

If not, consult a local RV repair facility to have it taken care of.

Problem 7: RV Air Conditioner Freezing Up From High Humidity

Without getting too far into the weeds here, your RV’s air conditioner pulls moisture out of the air to cool it before blowing it into your cabin.

Considering that fact, the higher the humidity, the harder your A/C unit has to work to cool the air.

The more moisture in the air, the more moisture that can freeze on the coils – simple as that.

The best way to combat this is to run your A/C unit on the high setting to keep the air flowing at a faster rate, or consider getting a small humidifier if you’re consistently camping in humid climates.

Opening your ceiling vents for 15-20 minutes at a time should also help mitigate this on particularly hot or humid days.

Problem 8: Freeze Sensor Is Bad Or Out Of Place

Some RV’s cooling units come with a freeze sensor that’s installed on the evaporator coil fins.

This sensor “sees” ice and shuts off the compressor so that the warmer air can defrost them or reverse the unit depending on the mode and model of your AC unit.

If the sensor is misplaced, fallen off, or is defective, it will no longer prevent your RV air conditioner freezing up.

Check to make sure that the sensor is placed about halfway up the evaporator coils and not dangling freely.

If it is placed correctly, consider replacing it as they usually run about $30-$50, so this could be a cheap fix for you.

This video does a great job on showing you how to replace or reseat an RV freeze sensor:

Problem 9: Weak Capacitor

The fan capacitor is very important because when it fails or malfunctions, the blower motor (which blows cool air into your RV) cannot start.

If the A/C compressor is running but the fan is not moving that cooled air away from the unit, the coils can freeze up.

Additionally, a weak or failed capacitor can eventually cause the compressor not to kick on at all, which will mean you have no A/C in your RV.

You can test the capacitor with a multimeter to see if the capacitor is bad or failing, and replace if you are comfortable doing so.  If not, take it to an RV service center to have this done.

Problem 10: Low Refrigerant Or Coolant

This is not a common issue, but there is the potential that the A/C unit in your RV is freezing up because it’s low on refrigerant.

This is rare, unless there’s a pinhole leak in your system somewhere caused by corrosion or vibration.

RV AC systems are called closed-loop systems, so there’s nowhere for you to add refrigerant yourself anyway.

Have this checked by an RV service center as a last resort.

How To Prevent Your RV Air Conditioner Freezing Up

RV air conditioner freezing up

Follow these tips to prevent your RV’s AC from freezing up:

Clean Your Return Air Vents And Filters

As your RV’s A/C unit pulls hot air in from outside, it can suck in animal hair, dust, and dirt, which will clog the air filters and eventually the coils, leading to an overworked unit that freezes up.

Park In The Shade

The lower the outside air’s temperature is, the less work your RV’s air conditioner has to do.  The air inside your RV will stay cooler longer too, keeping you more comfortable and making sure your RV’s air conditioner runs efficiently.

Switch To LED Lighting

LED lighting is cheap, easy to install, and puts off less heat than traditional lighting, which affects the temperature of the air inside your RV and also affects how often or hard your AC unit has to run to cool everything.

Why Does RV Air Conditioner Freeze Up? Conclusion

We hope you’ve followed this guide and were able to get the air conditioning in your RV working again.

Were there any extra tricks you tried or tips you have for others going through the process?  Let us know in the comments below.

While you’re here, check out our guides on the best RV outdoor kitchen mods and how to get through an RV one night freeze for more great RVing tips.

Leave a Comment