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HomeRepair HelpTrane Central A/C RepairTrane Central air conditioner won't turn on Repair
Trane Central air conditioner won't turn on
If your Trane central air conditioner won't turn on, the most likely cause is a failed transformer that is not supplying the 24-volt signal needed to activate the contactor. A defective furnace control board is the next likely cause, followed by dead wall thermostat batteries. If the display is blank, replace the batteries and try the system again. Also check for an incoming power problem at the furnace or air handler, including a tripped circuit breaker, blown fuse, or unit power switch that is turned off. If the AC unit is still not turning on, a faulty wall thermostat or thermostat wiring may not be sending the cooling signal through the thermostat wire to the control board and contactor. Testing 24 volts between the C and Y terminals requires a multimeter. Turn off power before removing panels, and do not work inside the furnace, air handler, disconnect box, or condensing unit unless you are qualified to handle 240V line voltage. Have a licensed HVAC technician diagnose energized circuits and replace electrical components when needed. Enter your Trane model number to find the exact replacement transformer, control board, thermostat, or other part for your central air conditioner.
01 - Trane 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 - Trane 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 - Trane 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 - Trane 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 Trane central air conditioner not turning on?
What should I check if my Trane thermostat is not turning on the AC?
How do I test the transformer, thermostat, or contactor when my AC will not start?
Could a bad Trane control board be why my air conditioner will not turn on?
How do I find the correct Trane replacement part for an AC that will not turn on?
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