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HomeRepair HelpMars Central A/C RepairMars Central air conditioner won't turn on Repair
Mars Central air conditioner won't turn on
If your Mars central air conditioner won't turn on, the problem is usually in the low-voltage control circuit that signals the condensing unit to start. The most likely cause is a failed furnace or air handler transformer, which supplies 24 volts to the thermostat and contactor. Next, a defective control board may prevent the contactor from receiving the cooling signal or stop power from reaching the blower motor. A dead wall thermostat battery is another common cause, followed by an incoming power problem such as a tripped circuit breaker, blown fuse, or turned-off service switch. Less commonly, the wall thermostat or thermostat wiring may fail to send 24 volts through the thermostat wire to the control board and contactor. These checks can help diagnose an air conditioner not turning on, AC unit not turning on, or outdoor AC unit not running. Replacing batteries and checking switches are generally DIY tasks, but testing or replacing a transformer, control board, thermostat, or contactor involves low- or high-voltage wiring. Turn off power at the disconnect box and circuit breaker, and have a qualified HVAC technician handle 240-volt work. Enter your model number to find the exact Mars replacement part for your central air conditioner.
01 - Mars 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 - Mars 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 - Mars 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 - Mars 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 Mars central air conditioner turn on?
What should I check if my Mars thermostat is not turning on the AC?
Why is my Mars outdoor AC unit not running when the thermostat is calling for cooling?
What if my Mars central air conditioner keeps tripping the breaker or has no power?
How do I find the correct replacement part for my Mars central air conditioner?
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