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Comfortmaker Central air conditioner won't turn off

When your Comfortmaker air conditioner won't turn off, a shorted contactor or a bad wall thermostat or thermostat wiring is the most likely cause, keeping a cooling signal on the yellow (Y) terminal even after the thermostat is set to Off. A shorted furnace control board or main control board can cause the same problem, though it is a less common cause, by continuing to send voltage to the outdoor condensing unit and making the air conditioner run constantly. The most likely cause is the furnace control board, followed by the furnace's main control board, which can develop a short and keep the contactor energized. A failed wall thermostat or thermostat wiring is another common cause of an air conditioner running constantly. If the thermostat's contacts stick closed, it can continue sending a cooling signal through the yellow (Y) thermostat wire even when the thermostat is set to Off. A shorted contactor is less common but can also keep the AC running after the control signal stops. This can appear as central air won't turn off, AC won't shut off, or an AC keeps running. Inspect the control board and thermostat for visible damage, and test thermostat continuity only if you are comfortable using a multimeter. Turn off power at the disconnect box and circuit breaker before inspecting components. The contactor and other outdoor unit parts involve potentially dangerous 240V electricity, so have a qualified technician handle line-voltage testing or repairs. Enter your Comfortmaker model number to find the exact replacement control board, thermostat, or contactor for your system.

01 - Comfortmaker 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 - Comfortmaker 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 - Comfortmaker 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 - Comfortmaker 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 - Comfortmaker 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 Comfortmaker central air conditioner turn off?
How do I test a Comfortmaker thermostat that is not turning off the AC?
Can a Comfortmaker AC contactor cause the air conditioner to run constantly?
Could the Comfortmaker furnace control board or main control board be keeping the AC on?
How do I find the correct Comfortmaker part for a central AC that won't turn off?

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