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How to Stop Your RV AC Or Heat Pump From Freezing Up

An air conditioner is simply a machine that moves heat from one place to another, also known as a heat pump. Most of the time, an AC moves heat from inside to outside, cooling the space. In the RV world, the term “heat pump” generally means an air conditioner that can work in reverse, moving heat from outside to inside. This heat movement works well until it freezes up. A frozen air conditioner can lead to a sweltering RV and expensive repairs if you don’t fix it soon enough. 

If you’re dealing with this right now, fear not. Today, we’re demystifying the causes of this chilling problem and exploring effective solutions to thaw your frozen RV AC. Let’s begin. 

What Does a Freezing Up AC Mean?

Before diving into the details, let’s clarify what a “freezing up” AC means. When we say an air conditioner is “freezing up,” we’re not referring to the refreshing cold air it should produce but a malfunction where ice covers the evaporator coils within the unit. This happens when the evaporator coils, the components that make the warm air chilly, become so cold that the condensation inside the AC freezes. This causes ice buildup, hindering airflow and the AC’s ability to cool the air.

Most of the time, an AC operates right above the limit of freezing the coils. However, certain conditions can cause the temperature to drop. This can happen both in AC or heat pump mode. In heat pump modes, freezing coils is actually normal. However, the unit has a special defrost mode to remove the frost. Freezing up is generally much more of a problem in air conditioning mode.

Pro Tip: Does the sound of your RV air conditioner get on your nerves? These are the Quietest RV Air Conditioners.

replacing an RV ac
if your AC freezes up too often, you might find yourself in this position replacing it!

What Causes My AC to Keep Freezing Up? 

Understanding the root causes of your RV AC freezing up is crucial for preventing it from happening again in the future. Here are some common culprits. 

#1 Inadequate airflow

Insufficient airflow is one of the primary reasons your RV AC may be freezing up. When warm air doesn’t flow over the evaporator coils as it should, the temperature inside the unit drops, leading to ice formation. Inadequate airflow can result from various factors, like a clogged air filter, closed or blocked vents, or even a malfunctioning fan.

#2 Low refrigerant levels

Refrigerant is the lifeblood of your RV’s air conditioning system. It absorbs heat from the indoor air and carries it to the condenser coils to release outside. If your RV AC is low on refrigerant, it can’t absorb enough heat and changes the entire pressurization of the system. This causes the temperature to drop too soon in the evaporator, freezing it up. As ice forms and blocks airflow to this section, the freezing moves along the evaporator, continuing the freezing. In the worst case, freezing can work back to the compressor and cause real damage.

While adding more refrigerant to your AC might seem simple, most professionals caution against this due to the risk of damaging the system. Your best bet is to consult a professional HVAC technician who can diagnose the issue, repair any leaks, and recharge the system with the correct refrigerant.

RV air conditioner
Low refrigerant levels in your RV air conditioner can cause the coils in it to freeze.

#3 Dirty coils and filters

Dirty evaporator or condenser coils and clogged air filters can significantly impact your RV AC’s efficiency. Dirty coils don’t allow the correct heat exchange, while clogged filters restrict airflow. Both contribute to an RV AC freezing up. Luckily, the solution can be as easy as cleaning the coils and replacing the filter. Remember that most manufacturers recommend replacing the air filter every one to three months. 

Pro Tip: Dirty coils and filters may be stopping your air conditioner from running well. Use our guide on How to Troubleshoot and Repair Your RV Air Conditioner to cool off quickly.

Dirty air conditioner filter
Dirty coils or filters can restrict airflow in your air conditioner and cause it to freeze up.

#4 Thermostat Or Sensor Issues

Most AC units have a temperature sensor in the evaporator that tells the AC if its temperature is too low. This sensor tells the compressor to shut down to prevent icing. If this sensor fails or is in the wrong place, it can cause icing.

A malfunctioning thermostat can also sometimes cause icing by causing it to run longer than necessary or at lower temperatures, leading to freezing issues. If you suspect that the numbers aren’t adding up, try testing your thermostat for accuracy and replace it if necessary. It’s a relatively inexpensive fix that can save you from the hassle of future repairs. 

sensor in RV Coil
This is an RV AC (a failed one) note the little sensor stuck into the evaporator in the lower left. If this fails or falls out it can freeze up.

#5 Exterior temperature factors

The outside temperature can also play a role in freezing your AC. If the exterior temperature is too low, the evaporator coils may freeze. Furthermore, running your AC on a high setting when it’s cooler outside can lead to freezing. Just be sure to keep an eye on the temperatures, especially at night, and avoid running the AC if temperatures lower. You can even use a programmable thermostat to maintain a comfortable temperature while preventing overcooling.

Motorhome with air conditioners installed
Be productive and regularly clean coils, change filters, and check for loose or damaged components on your A/C unit to prevent freezing.

How Do I Unfreeze My Air Conditioner Fast? 

If you find your RV AC is already freezing up, you’ll want to take steps to thaw it out quickly. First, turn off your AC to prevent it from freezing even more. Then, turn your fan setting to “on” to help circulate warm air over the frozen coils, speeding up thawing.

Now, wait for the fan to defrost the system. During this step, be patient; thawing out a frozen RV AC can take several hours, so give it time to defrost completely. While you’re waiting, you can inspect the AC unit for any signs of refrigerant leaks. We recommend contacting a professional technician for repairs if you suspect a leak.

Once your AC thaws, you can turn it back on. Just be sure the fan is on auto!

RV air conditioner and fan
Turn off your AC and turn your fan setting to “on” to help quickly defrost the RV system.

How to Prevent Your RV AC From Freezing Up 

Once you thaw your RV AC, the last thing you want is to deal with it freezing up again. Prevention is the key to avoiding the inconvenience and potential costs of repairing a frozen RV AC. You can keep your RV air conditioner functioning smoothly by conducting routine maintenance. This includes cleaning coils, changing filters, and checking for loose or damaged components.

Check the sensors and clean the coils if the unit continues to ice. Beyond these things, there is a chance that you have a leak in your system that will need professional service.

Keep Your RV Cool By Becoming an AC Expert 

Your RV’s air conditioning system is a vital component, especially during hot summer trips. By understanding the causes of a freezing RV AC and following preventive measures, you can ensure a comfortable and hassle-free journey. Regular maintenance will keep you cool and extend the life of your unit, saving you from costly repairs. So, don’t let the heat ruin your adventure – take control of your RVing experience by becoming your own AC expert!

Do you do your RV maintenance? Let us know in the comments below! 

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About Tom Morton

Tom, a Pacific Northwest native, is our technical genius. Born in Washington and raised in Alaska before settling in Michigan. He's the man who keeps our operation running, both figuratively and literally.

With a background in Electrical Engineering, Tom specializes in RV solar systems and lithium batteries. He made history as the first documented individual to use a Tesla battery module as an RV battery. Tom has personally assisted countless RVers with system installations and has educated thousands more through his videos and articles.

Cinematography is another of Tom's passions, showcased in his work on the Go North series. You can see his camera skills on display in The RVers TV show on Discovery Channel and PBS where he also stars as a co-host.

Tom's mechanical expertise extends beyond RVs to boats, planes, and all things mechanical. He's renowned for taking on maintenance and repair projects single-handedly and is often spotted underneath RVs, making him the technical backbone of our endeavors.

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Charles Land

Friday 17th of November 2023

In humid weather, especially at night, turning the thermostat to the coldest position and the fan to the lowest position can cause icing. Just turn the thermostat up enough that the compressor cycles on and off will prevent icing - assuming that there aren't other issues you described.

Kevin Mezo

Friday 17th of November 2023

I do all of my own work on my 2018 35 foot heritage glen ltz trailer. The only tasks I don’t do are to refill refrigerant into the Ac systems, to grease axles, and change to new tires.