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HomeRepair HelpTrane Central A/C RepairTrane Central air conditioner won't turn off Repair

Trane Central air conditioner won't turn off

If your Trane central 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. A shorted board can continuously send voltage to the outdoor condensing unit, making the air conditioner run constantly even when the thermostat is set to off. The main control board is the next likely culprit and can produce the same symptom. If both boards appear undamaged, test the wall thermostat and wall thermostat. A thermostat with stuck electrical contacts may keep sending a signal through the yellow Y thermostat wire to the contactor. With power safely disconnected, a multimeter can check for continuity between the C and Y terminals while the thermostat is off. A shorted contactor is less common but can keep the condensing unit energized after the control signal stops. Because the contactor and outdoor unit contain 240V line-voltage circuits, shut off the circuit breaker and disconnect box before inspection, and have a qualified HVAC technician handle energized testing or electrical repairs. No refrigerant handling is needed for these checks. Enter your Trane model number to find the exact replacement control board, thermostat, or contactor for your central air conditioner.

01 - Trane 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 - Trane 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 - Trane 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 - Trane 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 - Trane 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 Trane central air conditioner turn off?
How do I test a thermostat when the AC won't shut off?
Could a contactor cause my air conditioner to keep running?
Should I replace the Trane control board if my central air won't turn off?
How do I find the correct replacement part for my Trane AC?

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