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GrandAire Central air conditioner won't turn off

If your Grandaire central air conditioner won't turn off, the system may be receiving a continuous cooling signal even when the thermostat is set to Off. The most likely cause is a failed furnace control board, which can short and keep sending voltage to the central air condensing unit. A shorted main control board can cause the same problem. Next, check the wall thermostat or thermostat wiring. Stuck electrical contacts between the common "C" and yellow "Y" thermostat wire terminals can continuously energize the condensing unit's contactor. If the thermostat tests good, a shorted contactor may be keeping power connected to the compressor and condenser fan. This can leave your air conditioner running constantly, waste energy, and overwork system components. Turn off power at the disconnect box and circuit breaker before inspecting parts. Testing or replacing a contactor involves dangerous 240V line voltage, so have a qualified HVAC technician handle that work if you are not trained. These repairs do not normally involve refrigerant handling or EPA 608 certification. Enter your GrandAire central air conditioner model number to find the exact control board, thermostat, or contactor replacement part for your system.

01 - GrandAire Central Air Conditioner Control Board

If the furnace control board has a short, it may be providing continuous voltage to the central air condensing unit preventing it from turning off. Inspect the control board for any damage and replace if necessary.
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Common

02 - GrandAire Central Air Conditioner Main Control Board

If the furnace's main control board has a short, it may be providing continuous voltage to the central air condensing unit preventing it from turning off. Inspect the control board for any damage and replace if necessary.
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Common

03 - GrandAire Central Air Conditioner Wall Thermostat

The wall thermostat has electrical contacts that send signal voltage back to the control board and the condensing unit's contactor to run the central air system. If the contact that controls the contactor sticks closed, it will send continuous voltage to the contactor, causing the central air system to run continuously. To determine if the thermostat is defective, use a multi-meter to test it for continuity. If the wall thermostat shows continuity between the common (“C”) and yellow (“Y”) thermostat wire terminals when the thermostat is in the off position, the thermostat has failed and will need to be replaced.
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Common

04 - GrandAire Central Air Conditioner Wifi Thermostat

The WiFi thermostat has electrical contacts that send signal voltage back to the control board and the condensing unit's contactor to run the central air system. If the contact that controls the contactor sticks closed, it will send continuous voltage to the contactor, causing the central air system to run continuously. To determine if the thermostat is defective, use a multi-meter to test it for continuity. If the WiFi thermostat shows continuity between the common (“C”) and yellow (“Y”) thermostat wire terminals when the thermostat is in the off position, the thermostat has failed and will need to be replaced.
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Common

05 - GrandAire Central Air Conditioner Contactor

The furnace control board sends a low voltage signal to the contactor. When the contactor receives the signal from the control board, it closes the circuit, sending voltage to the condensing unit components. If the contactor has shorted, it can send continuous voltage to the condensing unit's components resulting in the central air system not turning off. To determine if the contactor is at fault, use a multimeter to test the contactor for a short. If the contactor has shorted, replace it.
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Less Common

Frequently Asked Questions

Why won't my GrandAire central air conditioner turn off?
How do I test a thermostat that is not turning off the AC?
Can a bad AC contactor cause the condensing unit to keep running?
Could a GrandAire control board be causing the air conditioner to run constantly?
How do I find the correct GrandAire part for an AC that won't shut off?

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