Why Does My RV AC Freeze Up: 6 Main Causes And Solutions

Last updated on April 9th, 2019 at 10:51 am

Sitting in a RV for more than 30 minutes becomes extremely tough with poor ventilation. Which is why having a well functioning air conditioning system is just plain necessary. One of the common issues usually seen is RV ACs freezing up. So why does that happen?

There are 6 main causes for your RV AC freezing up:

Evaporator coils are dirty
Excess humidity
Faulty thermostat
Low freon levels
Short circuiting of supply and return air
Dirty condenser coils

Given my research into the common causes shared by people with a frozen RV AC, this list seems to cover 99% cases. If your RV AC doesn’t exhibit any of the above issues and still is frozen up, yours may just be a faulty piece that needs replacement. Basically, you’ll need a professional to take a look.

Keeping the 1% aside, let’s look into the 5 main causes why your RV AC may freeze up:

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#1 Dirty Evaporator Coils

If you remove the AC vent inside your RV, the coils you’ll see are called evaporator coils. The evaporator is responsible for cooling the hot air from inside the RV. However, over time, dirt, lint and dust tends to accumulate on the coils which makes them work harder and may even lead to freezing.

The best way to take care of this is to clean the evaporator coils with a brush to remove any dirt and then run the AC fan on high. On doing so, you’ll notice that the ice starts to melt and water will start to drip down from the vent. Be sure to place an empty bowl underneath!

Also- in case you’re not sure how an evaporator coil looks, take a look at this YouTube video demonstration of cleaning the evaporator coils

#2 Excess Humidity

If you’re in an excessively humid area, your RV Air Conditioner is probably freezing up because of that.

As the hot, humid air is sucked into the vents and cooled by the evaporator coils, the moisture condenses and gets frozen, which blocks the functioning of the Air Conditioner.

A really common sense hack that I came across in this YouTube video was to buy and install a dehumidifier inside your RV. Most dehumidifiers are sized appropriately for the average indoor home, such that if you’ve placed one in the living area, it’ll be effective for the entire area.

I liked this portable dehumidifier on Amazon. It's got over 2700 reviews at the time of writing this article, 81% of which are positive. It's quite affordably priced as well. If you go to the review section, you'll even find a couple of RV owners talking about how it worked for them.

#3 Faulty Thermostat

The thermostat is the electronic circuit that continuously keeps checking the temperature output of the air conditioner and regulating it. However, if your RV Air Conditioner has a faulty thermostat then things could very well go haywire.

Now, the Air Conditioner compressor won’t know when to stop. Hence, the cooling will continuously be on, leading to excessively low temperatures, and ultimately a frozen RV Air Conditioner.

If this is the case, you’ll need to remove the thermostat and replace it. Professional help may or may not be required depending on how savvy you are with appliances on board the RV.

#4 Low on Freon

If your AC is low on freon, that is the refrigerant liquid responsible for cooling down the hot air, that may be another reason why your RV air conditioner is freezing up. You’ll have to get someone to add freon to the air conditioner again.

However, in most cases being low on freon means there is a leak, which in turn means that you’ll need to replace the AC unit altogether.

#5 Short circuiting of supply and return air

The supply vent of the air conditioning system supplies cool air while the return vent sucks in hot air. If these two get short circuited somehow, it could be causing the air conditioner to freeze up.

This happens in RV refrigerators as well. If you leave the gasket on the RV fridge door isn’t sealing the door correctly, it provides a inlet for the hot, outside air to flow into the refrigerator and mix with the cold inside air- leading to certain spots inside the fridge that get frozen.

The exact same principle applies here. You should check the partition between inlet and outlet air sections in the ceiling. A short circuit could be easily repaired by some caulk or weatherproof tape, like this one on Amazon. Won't set you back by more than a couple of bucks

#6 Condenser coils are dirty

The condenser unit is mostly placed on the top of the RV, and you’ll have to climb on the roof to access it. It is responsible for throwing off heat from the inside of the RV to the outside environment and cooling the refrigerant vapor down back into a liquid.

Since it is exposed outside, the conditioner coils tend to get dirty which affects the refrigeration process. As we saw earlier with dirty evaporator coils, this may lead to the Air Conditioner freezing up as it has to work harder. This also means increased electricity usage, which already is a very precious resource for RV owners while they’re on the road.

Here’s what you do:

Use an air conditioner fin comb or a plain old screwdriver for scraping away any dirt that may have accumulated. You can also use a vaccum alongside to speed up the process. Sometimes, the fins of the condenser coil also get bent a bit here and there over time, so you can use the fin comb or screwdriver to straighten them as well.

#7 This Happens Sometimes Too

Bird nest or animals finding a home in/around the condenser fins can cause a ventilation issue leading to your air conditioner freezing up. It may seem like a silly inclusion on this list, but a quick look by climbing on the roof of your RV may just save you a lot of time!

How does the RV AC Work?

In case you don’t already know, here’s a quick and concise everything-you-need-to-know:

Hot air from inside the RV is sucked into the return vent and passes through the evaporator coil. The evaporator cools the air down and further lets the cold air pass into the supply vent. This cooling occurs by transferring the heat from the air to the refrigerant liquid, which gets converted to vapor form.

The heated refrigerant gas goes to the condenser coil, usually placed at the top of the RV. Here, the refrigerant gas cools down it’s heat is expelled to the outside environment. The liquid refrigerant is then routed back towards the evaporator through tubes, and the cooling cycle continues

Few Parting Tips On How To Maintain RV ACs

#1 Always ensure you clean your return air vent filters. As they suck in the hot air from inside the RV, they also tend to suck in dirt, dust, dog hair… you get the picture. Dirt is the enemy of proper air conditioner functioning, as I’m sure I have repeated enough times in this article- so do clean your return vent filter out every month or so.

#2 Install LED lights. LED lights run cooler than traditional lights and hence you get a small but significant decrease in on board temperature.

#3 Keep your RV parked in the shade as much as possible. The difference in temperatures is obviously significant and your air conditioning will work SO much better.

Conclusion

Think I missed anything in this post? I want your opinions in the comment section below! We read all comments at RV52 and would be happy to include your suggestions into the post for future readers.

Until then, stay cool!