6 Reasons Your RV Air Conditioner Freezes Up (With Fixes)

This post contains affiliate links.

On a recent road trip, our RV’s air condition froze at the worst possible time! It left us hot and grumpy in our RV while it defrosted and we scrambled to figure out what to do. After this, I looked up some handy fixes for these small air conditioners and ways of preventing this from happening again.

So, why do RV air conditioners freeze up? The top reasons an RV air conditioner freezes are:

1. dirty evaporator and condenser coils
2. bad flow dividers,
3. dirty air filters
4. high humidity
5. broken thermostat
6. low refrigerant

Turns out our poor air conditioner was just very dirty! This is the most common reason freezing occurs but there are several other possible culprits. Keep reading for how to clean your air conditioner coils as well as how to fix other issues you might face with your RV air conditioner.

Defrosting Your Air Conditioner

Before we can look at reasons why your air conditioner froze in the first place we need to defrost the unit. Defrosting is easy to do but it’ll take some time and may get a bit messy.

1. Inside the RV, remove the cover of the air conditioner unit using a screwdriver. Keep the screws in a safe place.
2. Turn the air conditioner fan on – not the cooling feature. Use the high setting to melt the ice over a period of a few hours.
3. Place the bucket beneath the air conditioner to catch dripping water as the unit defrosts. Place a towel under the bucket for extra protection.
4. After the unit is defrosted, let it dry overnight with the bucket and/or towel still in place to catch residual moisture.

Ideally, the drip pan of the air conditioner will catch all the water as the ice defrosts but its better to be safe and have a backup plan in place.

Reason 1: Dirty Condenser or Evaporator Coils

The majority of RV A/C freeze ups are caused by low airflow, usually due to dirty evaporator or condenser coils. The coils in your air conditioner unit—evaporator coils and condenser coils—need to be cleaned regularly. If either set of coils is dirty the air conditioner needs to work harder to cool the air and transfer heat out of the RV. The evaporator coils take the heat out of the air in the RV and the condenser coils expel that heat to the outside.

If your coils are dirty then there is less surface area available to allow this heat exchanging process to occur so your unit will have to work extra hard to keep things cool. Ice will build up on the coils since the system has to work harder due to reduced airflow. Cleaning your dirty air conditioner coils is the first step to make sure the unit isn’t overworking itself.

How to Clean Evaporator and Condensor Coils

The evaporator and condenser coils are contained within the air conditioner up on your roof. The evaporator coils are at the front of the unit underneath the shroud and located within a sheet metal housing. The condenser coils should be visible once the shroud is removed or even before depending on the model. To get started you’ll need a screwdriver, shop vac, soap, spray bottle, and a soft brush.

Step 1: Power Off

Before you climb up on the roof you will want to disconnect power to the air conditioner, unplug your RV or turn off your generator then disconnect your batteries. Alternatively, you could pull the fuse and turn off the breaker for the air conditioner. Just make sure there is no 12V or 110V power going to your air conditioner (your air conditioner’s controller uses 12V)

Step 2: Remove Covers

Start by removing the shroud on your air conditioner. There should be a couple of screws holding it in place. Once the screws are removed keep them in a safe place and remove the shroud.

Pro Tip: Bees and Wasps like to make nests under the air conditioner shroud. Be careful when you are removing the cover especially if you see any buzzing around.

With the shroud removed you can now see the condenser coils at the back and sheet metal housing for the evaporator coils at the front. Unscrew and remove the sheet metal housing. You’ll want to be careful of the gasket since this seals out the elements from getting into your RV through the air conditioner. Gloves are also recommended when handling sheet metal since the edges are very sharp.

Step 3: Vacuum the Coils

Before vacuuming you’ll want to block any openings in the air conditioner that lead down into the RV. This is to prevent dirt, debris, and cleaner from getting inside.

Then, you’ll vacuum both the evaporator and condenser coils using a soft brush attachment on your shop vac. Be gentle when working on your coils as the aluminum fins can be easily bent.

Step 4: Clean the Coils

I hate using aerosols and chemical cleaners so I opted to use a mixture of soap and water in a spray bottle over an aerosol coil cleaner. Mix your soap with water in your spray bottle and spray down both the evaporator coils and the condenser coils.

Once the coils are good and wet let them sit for a few minutes then wipe down with a soft brush or cloth. Vacuum the coils again to pick up any debris that was dislodged.

Step 5: Repeat if Necessary

If your coils were exceptionally dirty or it’s been a long time since they were cleaned it’s worth repeating the process of vacuuming and washing the coils again.

Step 6: Inspect Coils

Now that your coils are clean it’s the perfect time to inspect them. Check for any bent or damaged fins. Bent fins will reduce the efficiency of your air conditioner since they will reduce the airflow.

If just a few are bent you can straighten them with a thin knife or screwdriver. If you notice multiple fins that are damaged you can pick up a fin comb like this one on Amazon.

Step 7: Dry and Reassemble

While you are letting your coils dry you should also clean the shroud. Just a quick scrub with soap and water should do the trick and it’s also the perfect time to dislodge any “guests” that have made a home under the shroud.

Once everything is dry you can reassemble your air conditioner. Reinstall the sheet metal shroud replacing the gasket if necessary. Then screw the shroud back in place. Hopefully, this will resolve your air conditioner freezing issue.

These steps might be time-consuming, but it is an easy process to clean evaporator coil in an RV air conditioner. Make sure you do this each year—or each season—depending on how often you use your RV.

Below is a helpful video about how to clean your evaporator coils.

Reason 2: Bad Flow Divider

As I said above the main cause of an air conditioner freezing is poor airflow, another cause of this is a bad flow divider. A flow divider, also known as a baffle, keeps the hot inlet air separate from the cold outlet air.

If the baffle is not positioned properly or poorly sealed the cold air outlet could be leaking into the hot air inlet which means the air entering the air conditioner is already cold and the unit would try to cool it even further causing ice to form.

This is usually an easy fix by repositioning the flow divider. You can seal the divider in place with some HVAC foil tape to prevent this from happening again in the future

Reason 3: Dirty Air Filters

Again we are talking about airflow. If the return air filters are dirty then the airflow intake will be reduced and could be causing your ac unit to freeze.

The air filter needs to be cleaned out monthly during RV season. Wipe any visible debris and wash with soap and water. If you have time, you can soak it for 10-15 minutes in a vinegar-and-water solution (one part vinegar to nine parts water) and leave it to air dry overnight before replacing it.

Be sure to replace your dirty air filters each year, as well. Small spaces like an RV are full of dirt and debris so having good air filters are important for you and your air conditioner’s health. The foam filters can be found in home improvement stores and on Amazon for as little as $5. You can purchase RV specific ones or simply cut standard ones down to size.

Here are some tips to using an air purifier to improve RV air quality.

Reason 4: There Is Too Much Humidity In The Air

Humidity is a huge factor in how well your RV air conditioner functions. This is because when the air is cooled the humidity condenses out of the air and should drain off your roof. Here’s why your RV air conditioner leaks when it rains.

On humid days, your ac unit is trying desperately to keep up, but the moisture in the air is too much for the evaporator coil to handle. If the fan is running on low the water can start to freeze on the coils since there is just so much moisture.

Running your fan on high in high humidity areas might just be enough to keep the air flow moving fast enough to prevent freezing from occurring. Otherwise, you can try cleaning your air conditioner and dirty air filters if you haven’t done so recently which might help.

If you enjoy hot and humid places, like Florida and Georgia, then investing in a dehumidifier will certainly help. A dehumidifier will take moisture/humidity out of the air so your air conditioner won’t have to work as hard.

Small dehumidifiers are also available for smaller spaces. For example, this highly-rated SEAVON dehumidifier, on Amazon, is marketed for RVs. Investing in a dehumidifier is cheaper than having your air conditioner serviced or being stuck in hot humid weather without an ac unit.

You can also open ceiling vents for a limited time on humid days. 10-20 minutes should do the trick to help some of the hot air and moisture escape.

Humidity can’t always be avoided, but it can at least be remedied. Invest in a small dehumidifier and ventilate your RV to improve air flow and lighten the load on your small air conditioning unit.

Reason 5: The Thermostat Is Broken

If you find your air conditioner only works if you keep having to turn down the thermostat and you’ve ruled out the other possibilites, you may have a broken thermostat. Now, this is only applicable for A/C units with thermostat controls.

If your thermostat is an older unit then changing it is probably a good idea anyway since the old slider styles are notoriously inaccurate for temperature readings.

Follow the quick steps below to double-check your thermostat reading:

1. Check the temperature with a thermometer reading.
2. Compare it to the temperature reading on the thermostat. If they are approximately the same, it’s not the thermostat.
3. If the reading is different, the RV’s thermostat is malfunctioning.

Replacing a thermostat isn’t overly difficult but you should be comfortable doing minor electrical work. If you aren’t, hire a professional to ensure the job is done properly and safely. Here are the details on using a household thermostat in your RV.

Reason 6: Low Refrigerant

Low refrigerant could be the cause of your freezing issue but most likely it’s not the problem. RV air conditioners are factory sealed (hermetic) which means its a closed-loop system so unless you have a leak somewhere you won’t be losing any refrigerant.

Also, since they are a closed system there is nowhere to add refrigerant if you suspect this is the issue. Some technicians will install a service port in order to add refrigerant but frequently, for the amount of work involved, its cheaper to get a new unit.

If you have a newer RV definitely look at your warranty and see if you are still covered. If your newer A/C is freezing and you’ve cleaned your coils hopefully your warranty will cover replacing the unit

Other Common Problems With RV Air Conditioner Units

It’s possible to have other trouble with RV air conditioners as well (aside from freezing). Let’s discuss the other issues you might face—as well as the remedies.

The Unit Blows Hot Air

If the air conditioner in your RV blows hot air instead of cool air you’ll want to confirm the compressor is turning on. If it’s not turning on then it’s likely a power issue.

If the fan is running but the air isn’t cooling make sure it’s not as simple as the cooling function is off. If your unit is on auto then you might just need to turn the thermostat down to get it colder.

If the compressor is coming on then you’ll want to check for proper airflow. Many of the above checks would apply like making sure your coils and filters are clean.

Another possibility is the air conditioner is low on refrigerant. As mentioned above this is basically a death sentence for an RV air conditioner. Having a technician add more refrigerant will likely cost more than just replacing it.

The Unit Is On But The Fan Isn’t Moving

There is a small fan inside the air conditioner system in your RV. It propels cold air through the system and into the rooms of your RV. If the fan isn’t running then hopfully it simply needs a little oil to start running again.

To access the fan you’ll need to get up on the roof again and remove the shroud. Make sure all power is disconnected from the air conditioner then spray it with a small amount of WD-40 or other similar products. Move the fan gently and spray a little more on the areas that were previously covered. If necessary, dab off any excess oil.

Turn the unit on again, and it should be fixed!

The Air Conditioner Won’t Turn On

Sometimes air conditioner units simply won’t work. There are two possible reasons for this.

The first possible reason the air conditioner (or anything else in the RV for that matter) won’t turn on is that you used too many electrical appliances at once. This can be an issue if you are using your generator or even if you are plugged into shore power.

Running several power hogs at once, like the air conditioner and microwave might not be a good idea. Avoid using multiple devices with large current draws at the same time.

Another real possibility the air conditioner won’t turn on is because the unit completely gave out. Every appliance gets to a point when the components inside start to fail. Here’s what to do if your air conditioner just hums.

Be sure to check what your warranty covers if you have a newer RV. If your RV is a new purchase, this and other repairs might be covered free of cost to you. If this is the case, don’t try to fix anything yourself because it might void the warranty entirely.

In the event that your older RV’s air conditioning doesn’t make cold air (and isn’t covered under warranty), you should turn to a professional RV mechanic and/or dealership to install a new unit for you. Though it might be an inconvenience for you and your wallet, professionals will be able to get your RV back to normal temperatures for you in no time.

These are some of the common problems you might face with your RV’s air conditioner. Solutions here can be simple, but they vary in cost. Whether you’re able to fix them yourself or need to bring in the professionals, you’ll be back to your regular travels shortly.