The part(s) or condition(s) listed below for the symptom Heat pump 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.
A run capacitor stores and releases a charge to start and run the condenser fan motor. If the capacitor is defective, the fan motor might be noisy, overheat, or not run at all, resulting in the unit not cooling. To determine if the run capacitor has failed, inspect the capacitor. If the dual run capacitor is bulging or leaking, replace it.
A dual run capacitor stores and releases a charge to start and run 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, resulting in the unit not cooling. To determine if the dual run capacitor has failed, inspect the capacitor. If the dual run capacitor is bulging or leaking, replace it.
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.
Since the blower motor is the component that circulates the cooled air through the home's venting, a defective blower motor will result in the unit not cooling. You can use a multimeter to test the blower motor for electrical continuity, a continuous electrical path present in the motor, as well as determine if power is reaching the motor. You can also try turning the blower wheel by hand. If the wheel does not turn freely, it's likely the motor bearings have seized and the blower motor will need to be replaced.
Since the circulation blower fan motor is the component that circulates the cooled air through the home's venting, a defective motor will result in the unit not cooling. You can use a multimeter to test the motor for electrical continuity, a continuous electrical path present in the motor, as well as determine if power is reaching the motor. You can also try turning the blower wheel by hand. If the wheel does not turn freely, it's likely the motor bearings have seized and the motor will need to be replaced.
The air handler 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 outside unit components. If the contactor is defective, it will not provide voltage to the outside 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.
The compressor is a pump which compresses the refrigerant and circulates the refrigerant through the evaporator and condenser coils. If the compressor is not working, the unit won’t cool. However, this isn’t usually the case. Before replacing the compressor, first check all of the more commonly defective components. If all of the other components are working properly, use a multimeter to test the compressor for continuity. If there is an open circuit, the compressor is likely defective. If the compressor is defective, it must be replaced by a licensed technician.
If the outdoor coil is clogged with debris, the fan will not be able to remove heat from the coil, resulting in a loss of cooling. The coil can be cleaned with a garden hose and spray nozzle from the inside out. If the coil is excessively dirty, a coil cleaner spray can be used to help loosen the dirt. Inspect the furnace or air handler air filter and replace it with a new one if the filter is dirty or hasn't been changed in the past six months.
If the outside unit contactor is not receiving 24 volts or power is not getting to the air handler blower motor, a possible cause is a defective control board. While this is not a common problem, if all other potentially faulty components are working properly, the control board should be replaced.
If the outside unit contactor is not receiving 24 volts or power is not getting to the air handler blower motor, a possible cause is a defective main control board. While this is not a common problem, if all other potentially faulty components are working properly, the control board should be replaced.
The control board sends a low voltage signal of 24 volts to the contactor through the wall thermostat. When the contactor receives the signal from the control board, it closes the circuit, sending voltage to the outside unit components. There should be 24 volts between the common (“C”) and yellow (“Y”) thermostat wire terminals on the air handler control board when the wall thermostat is in the cooling mode. You can check for this voltage with a multimeter. If voltage is not reaching the contactor, it's likely the wall thermostat is defective and will need to be replaced.
The control board sends a low voltage signal of 24 volts to the contactor through the WiFi thermostat. When the contactor receives the signal from the control board, it closes the circuit, sending voltage to the outside unit components. There should be 24 volts between the common (“C”) and yellow (“Y”) thermostat wire terminals on the air handler control board when the WiFi thermostat is in the cooling mode. You can check for this voltage with a multimeter. If voltage is not reaching the contactor, it's likely the WiFi thermostat is defective and will need to be replaced.
If the unit has good air flow, the indoor and outdoor unit coils are clean, the fan and compressor are running, and the furnace or air handler blower is on, but there is still not enough cooling, it is likely there is a leak or restriction in the sealed system. Since diagnosing and repairing a sealed system takes specialized tools and knowledge, a qualified service technician should diagnosis and repair the unit.
The control board sends a low voltage signal of 24 volts to the contactor. When the contactor receives the signal from the control board, it closes the circuit, sending voltage to the outside unit components. Some air handlers have a separate transformer for the 24 volt circuit, so if the contactor is not receiving the proper voltage, it's likely this transformer has failed and the component will need to be replaced.
The outdoor heat pump unit is energized with 240 volts of electricity. The electricity flows through a disconnect box to the compressor and condenser fan motor. The disconnect box enables the heat pump unit to be turned off outside. The disconnect box 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 that supplies 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. Fuses that do not have continuity should be replaced.
For the heat pump to work properly, the wall thermostat should be set for "Cool" and the fan set for "Auto" or "Fan On". The temperature setting also needs to be set colder than the room temperature. When the thermostat is set properly, both the outdoor unit and the furnace or air handler blower should be running.
