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HomeRepair HelpLennox Central A/C RepairLennox Central air conditioner coil icing up Repair
Lennox Central air conditioner coil icing up
If your Lennox central air conditioner coil is icing up, the evaporator coil may be freezing because air is not moving properly or refrigerant flow is incorrect. First, check whether the furnace or air handler humidifier damper is open; it should be closed or set to summer mode so air cannot bypass the coil. Next, inspect the blower motor. A failed motor, seized bearings, or a blower wheel that does not turn freely can cause an evaporator coil frozen condition. A clogged or damaged blower wheel and housing can also restrict airflow and lead to AC icing over. If the blower motor will not run, a defective run capacitor or capacitor may be responsible. A failed thermal expansion valve, or TXV, can also cause an air conditioner freezing up by improperly regulating refrigerant into the evaporator coil. Turn off power before inspecting the blower, wheel, or capacitors, and use caution because capacitors and other components involve electrical hazards. TXV or refrigerant-related repairs require an EPA 608-certified HVAC technician and should not be attempted by DIYers. Enter your Lennox model number to find the exact replacement blower motor, blower wheel, capacitor, or other part for your central air conditioner.
01 - Humidifier Damper is Open
An open humidifier damper will let air bypass the evaporator coil. This loss of air flow can cause the evaporator coil to freeze up. If you have a humidifier on your furnace or air handler, confirm the humidifer damper is in the "summer mode" or closed position.
Highly Likely
02 - Lennox Central Air Conditioner Blower Motor
Since the furnace or air handler blower motor is the component that circulates the air through unit to cool it, a defective blower motor could result in the evaporator coil icing up. You can use a multimeter to test the blower motor for electrical continuity, a continuous electrical path present in the motor, as well as determine if power is reaching the motor. You can also try turning the blower wheel by hand. If the wheel does not turn freely, it's likely the motor bearings have seized and the blower motor will need to be replaced.
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Highly Likely
03 - Lennox Central Air Conditioner Blower Wheel and Housing
Over time the blower wheel and housing can become clogged with dust and debris. This will restrict the air flow which could result in the evaporator coil icing up. You can try cleaning the blower wheel with compressed air or with a soft bristle brush. Use caution when trying to clean the blower wheel as the fins are sharp and can be easily damaged. If the blower is damaged it will need to be replaced.
Common
04 - Lennox Central Air Conditioner Run Capacitor
If the run capacitor is defective, the blower fan motor may fail to run which could result in the evaporator coil icing up. To determine if the run capacitor has failed, test the capacitor with a multimeter. If the capacitor is unable to hold and release a charge or is bulging or leaking, replace it.
Common
05 - Lennox Central Air Conditioner Capacitor
If the capacitor is defective, the blower fan motor may fail to run which could result in the evaporator coil icing up. To determine if the capacitor has failed, test the capacitor with a multimeter. If the capacitor is unable to hold and release a charge or is bulging or leaking, replace it.
Common
06 - Lennox Central Air Conditioner Thermal Expansion Valve
A thermal expansion valve, commonly referred to as a TXV, regulates the amount of refrigerant in the evaporator coil to help maintain an optimal working temperature.
Common
Frequently Asked Questions
Why is my Lennox central air conditioner coil freezing up?
Can low airflow cause my evaporator coil to ice over?
How do I test the Lennox AC run capacitor when the blower motor is not running?
Does a TXV cause an air conditioner coil to freeze up?
How do I find the correct Lennox blower motor or capacitor replacement part?
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