Why Is My Air Handler Freezing Up?

Under normal operation, your air handler blows cool air in the summer and heated air in the winter. But occasionally, something goes wrong – your air handler is freezing up. You might notice that your cooling system is suddenly blowing warm air instead of cold air in the middle of a heat wave and start investigating.

When you locate the air handler in the attic, basement, or utility closet, you’re shocked to see:

• Visible icing of the evaporator coil or its cabinet
• Frozen refrigerant lines at the outdoor unit
• Air handler dripping water, and a puddle of water on the floor

These are all signs of a frozen evaporator coil.

Your air handler houses the evaporator coil, or “A” coil, so nicknamed because of its shape. The evaporator coil works with the condenser coil and other system components during the refrigeration cycle to cool your home during warmer months. If you have a heat pump, the cycle reverses in the colder months.

The safest thing to do is shut your HVAC system off. Go to your thermostat and switch it from COOL to OFF. Running the system with a frozen evaporator coil can cause major damage.

DO NOT chip away at the ice. This can damage the coil. Call your HVAC company to schedule repair service.

The biggest reason for frozen coils is restricted airflow. This can result from:

• A clogged or dirty air filter
• Blocked return air vents
• Dirty evaporator coil
• Low refrigerant/refrigerant leak
• Thermostat issues

When the HVAC technician arrives, they will check for all the possible causes of your frozen evaporator coil.  They may change the air filter and troubleshoot your thermostat if they think it’s part of the problem and clean the coil if it’s dirty.

Once the coil is clean, they will check the refrigerant levels and test for a refrigerant leak. That’s because the only way you would have low refrigerant is if there was a leak or the unit was improperly charged when it was installed. If they find an obvious leak, they will try and repair it. Lastly, they will recharge the refrigerant if necessary.

Your heat pump or air conditioning repair costs will vary depending on what caused the evaporator coil to freeze.

You can help prevent a frozen evaporator coil and other problems with regular air handler maintenance. Some you can do yourself, but you should leave other work to an HVAC professional.

Change the air filter every 30-90 days based on the quality of the filter. Your smart thermostat may display an alert when it’s time for a filter change. Otherwise, set a calendar alert on your phone. See our HVAC air filter maintenance guide for tips.

Keep your registers and return air vents clear. Keep the floor around the indoor unit clean and sweep away dirt, dust, and cobwebs. Keep landscaping plants at least two feet away from the outdoor unit to promote air circulation.

Schedule an HVAC service visit every spring to help your AC or heat pump run at peak performance all summer long. The HVAC technician will inspect the unit, clean the coils, and more.

Regular maintenance can help spot issues while they are still small and before they lead to big repairs. Sign up for an HVAC service plan, and the company will reach out to schedule appointments each spring and fall.

Finally, think about opting into Trane Diagnostics via the Trane Home App. This allows your Trane dealer to monitor your HVAC system remotely. They’ll receive alerts of any system issues and can act quickly to help you, even when you’re away from home on vacation.

Anne Fonda, Content Writer at Trane Technologies

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

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