Why Does My Air Conditioner Run on High Only?

Fan Speed

• It’s possible that your air conditioner is running on high because the fan speed is set high. Some units feature a “Fan Speed” or “Fan” button that increases or lowers the fan speed when pressed. If the fan is set to high while the air conditioner compressor runs, then the cold air generated by the cooling elements is pushed through the air conditioner vents at high speed. The fan can even run without the cooling element to circulate the air within the room. You can press the “Fan Speed” or “Fan” button to cycle to a lower fan speed.

Thermostat

• If the thermostat is defective or wired incorrectly, one of the air conditioner components might be permanently set to high. When the thermostat’s set temperature is met, both the air conditioner compressor and fan turn off, unless you have the air conditioner fan set to run without the compressor. It’s also possible that a faulty thermostat will fail to activate a component. You can raise the thermostat setting to a level above room temperature to test the thermostat. Once the thermostat setting is set to the higher temperature, the compressor and the fan should both turn off.

Temperature

• Hot outside temperatures may cause your air conditioner to run on high for long periods of time, possibly all day, depending on the thermostat setting. You can change the thermostat to a higher temperature to allow the air conditioner a break. Leaks in the home also force the air conditioner to run on high throughout the day with no breaks. Before turning on your air conditioner, you should confirm that all openings, such as open windows and unsealed cracks, are closed to prevent the leakage of cold air. If cold air is allowed to leak, the air conditioner will be unable to reach its thermostat goal and the unit will continue to run.

Wiring

• Poor or incorrect wiring from the circuit breaker to the air conditioner unit could cause the unit to run constantly, even after you turn it off or raise the thermostat setting. Before you inspect the wiring to the air conditioner unit, turn off the power at the circuit breaker. If you see that the wires at the air conditioner electrical panel are incorrectly connected, contact a technician to rewire the system.