Hi I have a heat pump heating unit in my 6 year house. Last night I got woken up by a loud squeek/grinding type noise it happen twice in the night. It also most sounded like a belt lose or something needs to be oiled. The nosie came from the unit that is outside. I never heard it do that before. The temp. stayed the same the unit did not shut off, but I ended up turning it off because I did not want to do damage to the unit. I have called repairman but he is not coming til this thursday. Is it alright if I turn it back on or should I wait to repairman? Also do I have to get this unit service once a year or should I?

Could be a motor bearing
Could be a over ice up condition or the defrost kicked in.
Best to just let it be so the service man can check it out. It is always possible to cause more damage by letting it run.

Sounds to me like a lack of maintenance on the fan motor, a few squirts of oil in the oil holes, if it has any might quieten it down for a while but sooner or later you will have to replace the motor.