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Comfortmaker Central Air Conditioner Condensing Unit Does Not Run

The part(s) or condition(s) listed below for the symptom Central Air Conditioner Condensing unit does not run are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.

Most Frequent Causes for Central Air Conditioner Condensing unit does not run

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Cause 1Compressor

Central air conditioners use a compressor to pump refrigerant through the condenser coils located in the outside condensing unit and through the evaporator coils mounted on top of the furnace or air handler. While it's not a common problem, if the compressor fails, the condensing unit will not run. You can use a multimeter to test the compressor for electrical continuity, a continuous electrical path present in the component, to help determine if the compressor is faulty. If all other potentially defective components, such as the capacitor and condenser fan motor, are operating properly, then a qualified technician should replace the compressor.

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Cause 2Wifi Thermostat

The WiFi thermostat has contacts in it that control the furnace. If the contact fails it can result in the furnace and the condensing unit to not run at all.

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Cause 3Condenser Fan Motor

A faulty condenser fan motor can be responsible for the central air conditioner condensing unit not running. You can use a multimeter to test the fan motor for electrical continuity, a continuous electrical path present in the motor, to help determine if the motor is defective. You can also use the multimeter to determine if power is reaching the motor. You can also try rotating the fan blades by hand. If the blades do not turn freely, it's likely the motor bearings have seized and the fan motor will need to be replaced.

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Cause 4Fan Motor

A faulty fan motor can be responsible for the central air conditioner condensing unit not running. You can use a multimeter to test the fan motor for electrical continuity, a continuous electrical path present in the motor, to help determine if the motor is defective. You can also use the multimeter to determine if power is reaching the motor. You can also try rotating the fan blades by hand. If the blades do not turn freely, it's likely the motor bearings have seized and the fan motor will need to be replaced.

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Cause 5Dual Run Capacitor

A dual run capacitor will power both the compressor and the condenser fan motor. If the capacitor is defective, the fan motor might be noisy, overheat, or not run at all. To determine if the dual run capacitor has failed, inspect the capacitor. If the capacitor is unable to hold and release a charge or is bulging or leaking, replace it.

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Cause 6Wall Thermostat

The wall thermostat has contacts in it that control the furnace. If the contact fails it can result in the furnace & condenser unit to not run at all.

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Cause 7Incoming Power Problem

The central air condensing unit is energized with 240 volts of electricity. This electricity then flows through the disconnect box to the compressor and condenser fan motor. The disconnect box enables the air conditioning unit to be turned off outside. The disconnect boxes includes a cartridge which may contain fuses. If the compressor and condenser fan motor do not run, the disconnect box fuses may have blown, or the circuit breaker supply power to the disconnect box may have tripped. To determine if the disconnect box fuses have blown, use a multimeter to test the fuses for continuity. If the disconnect box fuses do not have continuity, replace the disconnect box.

Cause 8No Power to Furnace or Air Handler

The furnace or air handler needs to have power reaching it for the central air condensing unit to run. If the control board has an indicator light, confirm the light is illuminated which indicates power is reaching the unit. If there is no power to the furnace or air handler, check the home's furnace or air handler's circuit breaker or fuse. Confirm the power switch on the side of the furnace is turned on.

Cause 9Run Capacitor

The run capacitor for the condenser fan motor and compressor might be at fault. If the run capacitor is defective, the fan motor might be noisy, overheat, or not run at all. To determine if the run capacitor has failed, inspect the capacitor. If the run capacitor is bulging or leaking, replace it.

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Cause 10Control Board

Control Board

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Cause 11Capacitor

The capacitor for the condenser fan motor and compressor might be at fault. If the run capacitor is defective, the fan motor might be noisy, overheat, or not run at all. To determine if the capacitor has failed, inspect the capacitor. If the capacitor is bulging or leaking, replace it.

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Cause 12Contactor

The furnace control board sends 24 Volts 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 is defective, it will not provide voltage to the condensing unit. To determine if the contactor is at fault, use a multimeter to check for 24 Volts at the low voltage side of the contactor. If 24 Volts is present but the compressor and condenser fan motor still won’t run, replace the contactor.

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