How to Stop Air Conditioners from Freezing Up


Just as there’s nothing better than an air-conditioned house on a hot day, there’s nothing worse than when your air conditioner suddenly freezes and stops working. There are several reasons why your AC unit may suddenly freeze up; learn how to prevent problems to keep your unit running well.

Refrigerant Charge

Your air conditioner may freeze due to the refrigerant charge either running low on fluid, or it may be improperly charged. This may mean you have a leak somewhere in the unit, either due to parts rubbing up against one another, or because some fittings and joints are a little loose, causing the refrigerant to run out.

In this case, call a qualified technician to service your unit. The tech can refill the fluid, fix any loose or broken fittings and joints, and perform maintenance to prevent potential leaks and freezing issues.

Restricted Airflow

Your air conditioner has a filter that helps to keep the air clean as it blows over the coils. The filter is necessary for two reasons: it helps keep your indoor air cleaner by removing things like pollen and dust, and it keep your unit from freezing.

When the filter gets too dirty, it can’t capture all of the particulates in the air. This means that dirt will slowly build up on top of your coils until they can’t work properly, which will drop the temperature of the unit too low. This in turn causes the unit to freeze.

To prevent this from happening, change your air conditioning filter often. Most units have a recommended timeframe for filter replacement (the type of filter you choose may also influence the timeframe). Stick to the recommended schedule to help prevent freezing and other issues.

Outdoor Temperature

It can be tempting to run the air conditioner and cool your house down for reasons that have nothing to do with the air temperature outside. Big parties with lots of people, a broken dryer vent, or just the kids fooling around with the thermostat can all raise the temperature inside your home even when it isn’t hot outside.

If you try to turn the air conditioner on when it is less than 60 degrees outside, however, this can cause your unit to freeze. Air conditioners aren’t meant to run at temperatures below 60, and the cold air blowing over the condensing coils will result in the coils freezing.

To stop this from happening, find other ways to cool down your home when the temperature drops outside, such as turning on a fan, or opening the windows.

Too Much Water

Your air conditioner produces water by pulling some of the humidity out of the air as it passes over the condenser. Part of this water is collected to help cool the air. The rest of the water is meant to drain out the back of the unit. If the water is unable to drain, however, either due to a clog or the unit not being positioned well for draining, the excess water will get tossed up onto the coils again and again. The water touching the coils will eventually freeze, and your unit will stop working.

When this happens, you need to investigate why your unit is holding onto water. Take off the cover and the filter and take a look inside. If you find a clog or some dirt or debris, clean out the inside of the unit to let the water flow freely. Otherwise, try tipping the unit backward slightly, away from the house, to help it drain better and prevent excess water accumulation.

Keep Your Unit Running Well

Regular cleaning and maintenance can go a long way toward preventing freezing. Have your unit serviced regularly, change the filter on schedule, and clean out any debris that makes its way inside. With just a little regular effort, you won’t have to worry about the coils freezing up anytime soon.

Precision Air & Plumbing September 5, 2017


We want to help you learn about about all things air conditioning and heating! Have any questions or want to see us write about something? Give us a call, chat, or email and we'll do our best to help you out.