Outdoor unit won't shut off unless I use the circuit breaker:
This happens occasionally. The thermostat reaches the desired temperature, the indoor unit shuts off, the air stops blowing, but the outdoor unit keeps on running. In the heating mode (if it's a heat pump) it could eventually shut off on a high pressure safety device. But in the cooling mode, it could run forever unless you turn the breaker off. And this will cause the indoor coil to freeze up into a solid block of ice, eventually the ice will build-up and travel all the way to the outdoor unit.
So what causes this? Only a few things, the most common of which is a stuck compressor contactor
- located in the outdoor unit. The contacts tend to get pitted-up. Eventually they can weld shut. This can cause serious damage to the system. It is good practice to replace the contactor every few years or when pitted - just like spark plugs in a car.
Another cause would be a shorted thermostat cable. This can be caused by a weed-whacker hitting the wire outside, or a wire-staple digging into the wire too tightly, rodents chewing on it, or just bad wire.
Lastly, the thermostat itself could be bad, sending a signal to the outdoor unit when it isn't supposed to.
Below is a list of possible causes. Items in red usually require a service call. Items in blue however can be addressed, some even fixed by the homeowner.
Red = Professional fix | Blue = Homeowner fix
The bottom causes in blue are commonly found problems and can be addressed by the homeowner. Try to check for these conditions first before calling for service.
Please keep in mind that the information found on our website is provided free of charge and Hannabery HVAC does not assume any liability resulting from the information we provide. We hope this information helps, but please note that these are just rough guidelines, and not all possible situations are covered. Your HVAC system should be inspected and repaired by a trained technician.