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HomeRepair HelpMiller Central A/C RepairMiller Central air conditioner coil icing up Repair
Miller Central air conditioner coil icing up
If your Miller central air conditioner has an evaporator coil frozen or is experiencing AC coil freezing up, shut the system off and let the ice melt before testing it. The most likely cause is an open humidifier damper, which allows air to bypass the evaporator coil; set the damper to summer mode or the closed position. Next, check the blower motor in the furnace or air handler. A failed motor or seized bearings can stop airflow, while a clogged or damaged blower wheel and housing can restrict airflow and cause your air conditioner to freeze up. A defective blower motor run capacitor or capacitor can also prevent the blower from running. Less commonly, a faulty thermal expansion valve, or TXV, can mismanage refrigerant flow and lead to AC icing over. Cleaning the blower wheel and checking the damper are reasonable DIY steps, but testing capacitors or motors involves electrical hazards, and 240V work should be handled by a qualified technician. TXV or any sealed-system repair involving refrigerant requires an EPA 608-certified HVAC technician. Enter your Miller central air conditioner model number to find the exact replacement blower motor, blower wheel, capacitor, or other part for your unit.
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 - Miller 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 - Miller 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 - Miller 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 - Miller 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 - Miller 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 Miller central air conditioner coil freezing up?
How do I troubleshoot a Miller AC blower motor when the evaporator coil is frozen?
Can a bad capacitor cause my Miller air conditioner to freeze up?
What should I do if my Miller AC coil keeps icing over after cleaning the blower wheel?
How do I find the correct replacement part for my Miller central air conditioner?
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