There are several reasons why your heat pump doesn’t start. Some solutions are easier than others.

Some simple fixes:

• Check the thermostat to see if it is set properly. If you have a smart thermostat, it can tip you off to the cause.

• Check the outside unit to see if it is blocked by ice, snow or debris that block operations.

• Look at the filter, which can get so dirty it derails the system.

• Another possibly simple fix: Did the circuit breaker trip? This can happen when a heat pump demands power. If this is the case, turn on the heat pump’s breaker. If the heat pump promptly resumes, the problem may be solved. But if it persists, you need to call a technician.

The next two solutions also can be complicated.

• If you hear a click when the heat pump refuses to turn on, the start capacitor is dead. That’s the device that helps the motor start.

• The next likely scenario: The reversing valve is stuck or broken, unable to switch between modes.