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HomeRepair HelpComfortmaker Central A/C RepairComfortmaker Central air conditioner won't turn on Repair
Comfortmaker Central air conditioner won't turn on
When a Comfortmaker central air conditioner won't turn on, the problem is usually in the low-voltage control circuit or the power supply to the furnace, air handler, or condensing unit. The most likely cause is a failed transformer, which should send 24 volts from the furnace control board to the thermostat and contactor. Next, a defective control board may prevent the contactor or blower motor from receiving power. If the thermostat display is blank, replace its batteries, then check for a tripped circuit breaker, blown fuse, or power switch turned off at the furnace or air handler. A failed wall thermostat or thermostat wiring is less common, especially if 24 volts is not reaching the contactor through the thermostat wire. These checks can help diagnose an air conditioner not turning on, an AC unit not turning on, or a central air conditioner that won't start. You can safely check thermostat batteries, switches, and breakers, but testing 24-volt circuits requires electrical knowledge. Turn off power before servicing, and leave any 240-volt wiring or condensing unit repair to a qualified technician. Enter your model number to find the exact Comfortmaker replacement transformer, control board, thermostat, or other part for your central air conditioner.
01 - Comfortmaker 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 - Comfortmaker 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 - Comfortmaker 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 - Comfortmaker 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 won't my Comfortmaker central air conditioner turn on?
What should I check if my AC thermostat is not working or the display is blank?
Why is my Comfortmaker outdoor AC unit not turning on when the thermostat is calling for cooling?
How can I test the transformer or thermostat when my central air conditioner will not start?
How do I identify the correct Comfortmaker replacement part for an AC that will not turn on?
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