Why Is My AC Unit Freezing Up?


The sweltering summers of Huntsville are the worst time to lose your air conditioning. If your air conditioner is freezing up and you’re not sure why, follow this check list to see if you can identify the problem.

First, it’s important to know the three overall causes for why your AC freezes up.

Why Air Conditioners Freeze Up

While there are other possible causes, your air conditioner most likely froze because of one of these three:

▪Restricted Airflow

▪Low Levels of Refrigerant

▪Thermostat or Outside Temperature Issues

Let’s take these one at a time. Some of these may be a quick fix, and others will need a service call. That’s why you should read through these and do what you can to see what’s freezing your AC unit.

Airflow Problems

The number one most common reason for a frozen AC unit is airflow problems. When air passes too slowly across the cooling coil, moisture accumulates and freezes. The first solution is to check for dirty air filters. If the air filter clogs up, then air won’t be able to pass through as fast. If the filter is clean, then the next place to look is at the ventilation. Are there blocks, obstructions or too many vents shut off? If so, then clear the blocks or open the vents. If there are no obstructions present, then it’s time to call in a professional.

Lost Refrigerant

The second most common reason for air conditioning freeze-ups is a loss of refrigerant. Refrigerant should not leak in well-maintained systems. However, under-serviced AC systems can leak due to wear and tear. If the refrigerant leaks out, then the coil will freeze. Likewise, you would notice an increase in your electric bill because the air conditioner works harder to produce the same level of cold temperature. Only a certified HVAC technician can replace refrigerant according to EPA guidelines.

Thermostat and Temperature Issues

A malfunctioning thermostat can also cause an air conditioner to freeze up. Many times, the problem arises in cold weather. If the AC freezes only at night, then that can be a clear signal of a thermostat issue. The cooling coil will naturally freeze if the air around it is too cold, as it depends on warmer air. Your thermostat should switch off at the correct temperature. If it doesn’t shut off and the AC continues to run, then you know you have a problem with the thermostat. This is especially true of very old models.

Bunn’s & Bennett Heating & Air Conditioning

If these suggestions did not solve your problem, or you’d simply prefer a professional take a look at your system, call Bunn’s & Bennett Heating & Air Conditioning. We are a licensed HVAC dealer serving the Huntsville-Madison (AL) and Tennessee Valley area. We are available 24/7/365 for any and all of your HVAC needs. Let us cool your Bunns!

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