The compressor on a window-mounted air conditioner is the component that works the hardest and gets the hottest, and sometimes, it overheats. To prevent damage to the compressor motor, some units have an automatic cutoff that switches off the power to the entire unit, and units with this feature often have a reset button. This button is usually red, and it may be quite small, but it's usually easy to find.
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The button is seldom mounted on the compressor itself because the compressor is buried deep in the machine and is inaccessible. The button is more likely to be found on the control panel or somewhere else on the front panel. If you can't find a reset button, your model may not have one, and you'll have to use a different method to reset the compressor.
Some air conditioners have a reset button that you press when the overload switch turns off the compressor. If there's no button, you can usually reboot the system by turning off the breaker for 20 to 30 minutes.
Why Air Conditioners Overheat
The compressor in a window-mounted air conditioner is at the back of the unit, which overhangs the outside of the building. The compressor's job is to pressurize the refrigerant as it flows through the condenser coils, which are right next to it, and this is a process that generates a lot of heat. The metal housing has louvers to allow this heat to dissipate, and if they get blocked by debris, the unit can overheat. Some other reasons for overheating and tripping the emergency power cutoff include:
- Dirty air filters.
- Dirt on the condenser coils.
- Defective condenser fan.
- Refrigerant leak.
- Ice on the evaporator coils.
Some of these problems are easy to fix, but some require professional repair, and the power will probably keep cutting out until the repair happens.
Before you press the reset button, it's important to unplug the machine and leave it unplugged for at least 15 seconds. After you plug it in, check the circuit breaker in the main panel that controls the air conditioner circuit to make sure it hasn't tripped. If it has, reset it.
The actual procedure for using the reset button varies slightly from model to model, so it's always a good idea to consult your owner's manual. In most cases, you push the button and hold it for at least three seconds, and when you release it, the unit should start. If it doesn't, try lowering the thermostat to its lowest setting to force the machine to start. If it doesn't start, check the breaker again, and if it has tripped, there's a problem that requires repair. Do not reset the breaker and turn off the air conditioner until the problem is fixed.
If the air conditioner doesn't have an emergency cutoff feature, it won't have a reset button, but it may still need to be reset. It can function erratically after a power outage or when it's used continuously for an extended period. The cause of the erratic behavior is often in the control panel, and like you do with a computer, you resolve the glitch by rebooting it.
Unplug the air conditioner, switch off the circuit breaker and leave the power off for a good 20 to 30 minutes. If overheating was the problem, this will give the unit time to cool down. To restore power, first turn on the breaker, plug the unit back in and test it to make sure it's running normally. If it isn't, call for service.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker and Family Handyman.