Why Do Air Conditioning Coils Freeze?

Air conditioners need good airflow moving through the equipment to keep coils warm and working correctly. When air isn’t freely moving across the evaporator coil, its temperature drops, leading to a frozen AC coil. A dirty air filter or restricted air movement in ducts could be preventing proper airflow.

Air conditioners require correct refrigerant levels to operate. When a refrigerant leak is present, refrigerant pressure drops while the system requires the same level of expansion. This creates a cooler temperature, dropping the coil temperature so it freezes.

All sorts of mechanical problems and other issues can cause an air conditioner’s coils to freeze. Moisture that is condensed by the cooling process freezes due to the coil’s low temperature before it can drain away, creating the ice you see on your cooling coils. This ice acts as an insulator, preventing the heat transfer that creates cooling.

Signs of a Frozen Air Conditioning Coil

If your air conditioning coils have frozen, you may experience the following symptoms:

• Air conditioner runs, but no cool air comes out in your home.
• There is visible ice on your indoor or outdoor coils.
• There is more condensation in your home or around your cooling unit, as frozen cooling coils create moisture buildup.

Troubleshooting a Frozen Air Conditioning Coil

If you have a frozen air conditioning coil, there are a few steps you should take to troubleshoot the problem before calling an HVAC repair company.

• Change your air filter. Many times, a clogged air filter is the reason behind frozen cooling coils. The air filter is filled with contaminants and restricts air movement through your cooling system. Change the filter to allow free-flowing air movement through the system.
• For air conditioners, switch the thermostat settings to off, but turn the fan to on. This will move air over the indoor coil, and starts to unfreeze it. It takes a few hours for a coil to unfreeze, so be patient.
• If you use a heat pump system, run its defrost mode to thaw out your coils. For air conditioners, follow our de-icing steps to thaw your unit.

Fixing Frozen Air Conditioning Coils

There are several potential causes for frozen air conditioner coils that require professional help. The following repairs are made by your local HVAC contractor to restore your coils’ function.

• Coil cleaning. Dirty coils prevent proper heat exchange, which may be the cause of your frozen coils. Your HVAC technician cleans the coilsof built-up dirt and grime to allow proper heat exchange for cooling.
• Refrigerant leaks. Your technician inspects the refrigerant system to find the source of leaks. Repairs are made and your system is properly charged to prevent the issue from happening again.
• Duct repairs. Damaged ductwork may prevent proper air movement through your cooling system. Your HVAC company repairs or replaces faulty ducts to prevent coil freezing.
• Drain clogs. If your cooling system’s condensate drain pan and lines are clogged, there will be extra moisture in your system which leads to coil freezing. Your technician clears the drain pan and lines of clogs that cause moisture backup.