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HomeRepair HelpRheem Central A/C RepairRheem Central air conditioner won't turn on Repair
Rheem Central air conditioner won't turn on
If your Rheem central air conditioner won't turn on, start with the low-voltage control circuit before replacing major parts. The most likely cause is a failed transformer, which supplies 24 volts from the furnace or air handler to the thermostat and condensing unit contactor. Next, a defective furnace control board may prevent the contactor from receiving the cooling signal or keep power from reaching the blower motor. If the thermostat display is blank, replace its batteries, then check for an incoming power problem, including a tripped circuit breaker, blown fuse, or power switch turned off beside the furnace or air handler. Less common causes include a failed Rheem wall thermostat or thermostat wiring, faulty thermostat wire, or a missing 24-volt signal between the C and Y terminals. You can safely check thermostat batteries and obvious power settings, but testing 24-volt circuits requires electrical knowledge. Turn off power before servicing, and have a licensed HVAC professional handle 240-volt wiring, the disconnect box, contactor, transformer testing, or control board diagnosis. No refrigerant work is indicated for this symptom. Enter your model number to find the exact Rheem replacement transformer, control board, or thermostat for your central air conditioner.
01 - Rheem Central Air Conditioner Transformer
The furnace control board sends a low voltage signal of 24 volts to the thermostat. When the themostat cooling contacts close, a 24 volt signal is sent to the contactor coil, closing the high voltage circuit and sending power to the condensing unit components. Some furnaces have a separate transformer for the 24 volt circuit, so if the contactor is not receiving the proper voltage when the thermostat cooling contacts are closed, it's likely this transformer has failed and the component will need to be replaced.
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Highly Likely
02 - Rheem Central Air Conditioner Control Board
If the central air condensing unit contactor is not receiving 24 volts or power is not getting to the furnace blower motor, a possible cause is a defective furnace control board. While this is not a common problem, if all other potentially faulty components are working properly, the control board should be replaced.
Highly Likely
03 - Wall Thermostat Batteries
Most wall thermostats are either powered by an enclosed battery or by the furnace or air handler transformer. If the thermostat display is dead, you can remove the thermostat cover and look for replaceable batteries. Replace the batteries if needed and check operation.
Common
04 - Incoming Power Problem
Check to see if there is power to the furnace or air handler. One or more indicator lights on the control board should be illuminated. If there is no power to the furnace or air handler, check to see if a circuit breaker has tripped or a fuse has blown. Confirm the power switch on the side of the unit is turned on.
Common
05 - Rheem Central Air Conditioner Wall Thermostat
The furnace 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 wall thermostat, it closes the circuit, sending voltage to the condensing unit components. There should be 24 volts between the common (“C”) and yellow (“Y”) thermostat wire terminals on the furnace 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.
Less Common
06 - Rheem Central Air Conditioner Wifi Thermostat
The furnace 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 WiFi thermostat, it closes the circuit, sending voltage to the condensing unit components. There should be 24 volts between the common (“C”) and yellow (“Y”) thermostat wire terminals on the furnace 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.
Less Common
Frequently Asked Questions
Why is my Rheem central air conditioner not turning on?
Why is my Rheem outdoor AC unit not running when the thermostat calls for cooling?
How do I troubleshoot a Rheem thermostat that is not turning on the AC?
Could the transformer or control board keep my Rheem AC from starting?
How do I find the correct Rheem central air conditioner replacement part?
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