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Central Air Conditioner Not Cooling

The part(s) or condition(s) listed below for the symptom Central air conditioner not cooling 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 not cooling

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Cause 1Contactor

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 is defective, it will not provide voltage to the condensing unit. To determine if the contactor is at fault, use a multimeter to test the contactor for continuity. If the contactor does not have continuity, replace it.

Parts
Cause 2Dual Run Capacitor

If the dual run 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 dual run capacitor is bulging or leaking, replace it.

Parts
Cause 3Incoming 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 4Run Capacitor

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.

Parts
Cause 5Condenser Fan Motor

To determine if the condenser motor is working, use a multimeter to test the incoming voltage to the motor. If the condenser fan motor is receiving the correct voltage but the motor still won’t run, inspect the capacitor to ensure that it is not at fault. If the capacitor is not bulging or leaking, replace the condenser fan motor.

Parts
Cause 6Capacitor

If the 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.

Parts