AC Troubleshooting: Frozen Air Conditioner

Frozen Air Conditioner Graphic

Logically, an air conditioning freezing up in the middle of a hot summer doesn’t make sense. But trust us, this happens a lot. In fact, it is one of the most common problems that lead to service calls.

There are two common issues that lead to a central air system freezing up in the summer. The first is inadequate airflow, and the second is low refrigerant.

The two primary causes of weak airflow include a dirty air filter or a dirty coil. When the cold refrigerant enters the evaporator coil, it absorbs the heat overflow and returns the warmed refrigerant to the outdoor condenser where it loses the heat. Without enough airflow, the refrigerant stays cold, and frost can form on the outside of the coil.

Changing filters on a regular basis will improve the airflow. An air conditioner needs warm air circulating around it to work properly.

If your refrigerant level is low or leaking, the coils become too cold and can freeze.

Common signs of a freeze up:

  • Your home is too warm
  • There is no air (or warm air) coming from the supply registers.
  • The filter is wet, or there are water leaks.

What to do if your air conditioner freezes up:

If you suspect that the coil is frozen, turn the system off immediately. Do not just adjust the thermostat to a higher temperature. If you allow the system to run, you risk damaging the compressor.

Next, call a certified HVAC company. No matter what the cause of the frozen coils, the system needs to be inspected to rule out refrigerant leaks.

While you are waiting for the coil to thaw, check the air filter. If it is dirty, replace it.

Check for air flow problems. Make sure that supply registers are open and that no furniture is blocking them. Also, check that the registers in storage places or unused rooms in your home are open. If too many are closed, your system may freeze up.

How to prevent it from happening again:

The most reliable way to prevent freeze-ups in the future is to have regular maintenance on the unit at least two times per year. We recommend scheduling maintenance before the startup of spring and after shut down in the fall.  When performing a maintenance on your system, our NATE certified technicians thoroughly clean and tune up your unit.

We also offer annual maintenance plans that include several benefits. As a maintenance customer, you receive an annual cleaning, inspection, and servicing of your unit, plus 15% off parts and labor, 24-hour emergency service with no overtime rates, and priority service. To learn more about our maintenance plans or to schedule maintenance, contact us.