Hello. The clicking sound could be as simple as dirt, dust, debris on the fan. Check the fan and if it needs to be cleaned do that first. It could also be the fan bearings. With the power off at the breaker, spin the fan to see if you can duplicate that clicking sound. If it appears, you will have isolated your problem and can remedy it by replacing the fan.

Finally, it could be that the refrigerant level is low. To check to see if that is the case requires two people. Recruit a helper who will turn off the breaker to the heat pump while you stand outside, near the heat pump. If the clicking continues for a few seconds after the power has been turned off you need to have your refrigerant recharged. Regards, Joe