I was looking at my friends heat pump because he said it was running all the time. I started at the fan relay and tstat no problems there. I was checking out the outside unit and noticed when it goes int defrost mode the fan didn't stop. I checked voltage to the reversing valve at the board and didn't have 24v. I pulled the disconnect and put it back in and the system started fine. Suction line was hot everything was good. I put it in defrost mode manually and the fan stopped reversing valve moved like its supposed to and had 24v to the reversing valve coil. I let it run normally and when it went in defrost mode on its own same thing happened, reversing valve moved but did not change back over and fan didn't stop. Anyone seen anything like this before, because I sure haven't? I'm thinking replace the board but I sure would like some suggestions.