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HomeRepair HelpMcQuay A/C RepairMcQuay Air conditioner won't turn off Repair
McQuay Air conditioner won't turn off
If your McQuay air conditioner won’t turn off, the problem is usually tied to poor heat transfer or a control part that is still sending power when it should not. Start with the condenser coils. Dirty condenser coils cannot release heat efficiently, so the AC runs continuously and the compressor may keep running as it tries to reach the set temperature. Next, check the temperature control thermostat, which can short and send constant voltage to the fan motor and compressor. A defective thermostat can cause the same air conditioner keeps running symptom if it does not open or close correctly. A dirty or damaged air filter can also reduce cooling capacity and make the unit run longer than normal. Less commonly, a failed thermistor may give the control board the wrong room-temperature reading, causing the air conditioner compressor running constantly. A relay board can also stick and keep voltage going to the compressor, but check the more common parts first. Enter your McQuay model number on RepairClinic.com to find the exact replacement part for your specific air conditioner.
01 - Condenser Coils are Dirty
The condenser coils dissipate the heat as the refrigerant passes through the coils. If the condenser coils are dirty, they won’t be able to dissipate the heat as effectively. As debris builds up on the coils, the air conditioner will become less efficient, causing the air conditioner to work harder to cool down. If the coils are significantly dirty, the air conditioner will not be able to maintain the proper temperature, and the compressor will run continuously in an attempt to cool the room. Check the condenser coils to determine if they are dirty. Refer to owner's manual for cleaning instructions.
Top Solution
02 - McQuay Air Conditioner Temperature Control Thermostat
The temperature control thermostat provides voltage to the fan motor and compressor. If the thermostat has shorted out, it might send continuous voltage to the compressor and cause the compressor to run all the time. To determine if the thermostat is shorted out, use a multimeter to test it for continuity. If the thermostat has continuity all the time, this indicates that it is shorted out and should be replaced. (Note: Some thermostats may also control a heater and, as a result, will have three terminals. Refer to your air conditioner’s wiring diagram for more information.)
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Highly Likely
03 - McQuay Air Conditioner Thermostat
The thermostat monitors the temperature of the air. When the air temperature rises above a set point, the thermostat activates a switch to provide power to the fan and compressor. If the thermostat is defective, it may cause the compressor to run continuously. To determine if the thermostat is defective, set the air conditioner to cooling and then use a multimeter to test the thermostat for continuity. If the thermostat does not have continuity while the air conditioner is set to cooling, replace the thermostat. (Note: Some thermostats may also control a heater and, as a result, will have three terminals. Refer to your air...
Highly Likely
04 - Dirty or Damaged Air Filter
A dirty air filter will greatly reduce the cooling capacity of the air conditioner, which may cause the unit to run longer than normal. Most air filters used in stand-alone air conditioners can be cleaned with soap and water. Only filters that are extremely clogged with debris or damaged will need to be replaced. Refer to owner's manual for guidance.
Common
05 - McQuay Air Conditioner Thermistor
The thermistor is a sensor which detects the room air temperature. It is connected to the control board. If the thermistor is defective it will not have continuity when it should. If this happens the compressor runs all the time.
Common
06 - McQuay Air Conditioner Relay Board
The relay board provides voltage to many of the air conditioner components, including the fan motor and compressor. If there is a problem with the relay board, it might provide continuous voltage to the compressor. However, this is almost never the case. Before you replace the relay board, make sure you check more commonly defective parts. If you are certain that all of the other components are working properly, replace the relay board.
Common
Frequently Asked Questions
Why won't my McQuay air conditioner turn off?
Can a bad thermostat make my McQuay AC run continuously?
What should I check if my McQuay air conditioner compressor is running constantly?
Can a dirty air filter cause an AC to keep running?
How do I find the right McQuay air conditioner thermostat, thermistor, or relay board?
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