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Mammoth Central air conditioner won't turn off

Won’t your Mammoth central air conditioner 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 control board can keep sending voltage to the outdoor condensing unit, making the central air run constantly even when the thermostat is set to Off. The main control board can fail in the same way and should be inspected for visible damage. Next, check the wall thermostat or thermostat wiring. A stuck contact between the common (C) and yellow (Y) thermostat wire terminals can keep signaling the condensing unit's contactor to run. With power disconnected, a qualified DIYer can test the thermostat for continuity while it is set to Off. A shorted contactor is less common but can also keep the AC running by continuously powering the condenser components. Because the control board and contactor involve electrical circuits, shut off power at the disconnect box and circuit breaker, and have a licensed HVAC technician handle any 240V testing or repair beyond your comfort level. Enter your Mammoth model number to find the exact replacement control board, thermostat, or contactor for your central air conditioner.

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

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