I have an intermittent problem with a Goodman heat pump. (Please forgive me for not having more information.) When I arrived the unit was in A/C mode, and the indoor unit was not running. The homeowner said the outdoor unit was running. Nothing I did with the stat would bring on the indoor fan. I removed the stat, check a few things and put the stat back on and the unit started and ran normally. What I get from the homeowner is that this will repeat. He installed a new stat thinking that was the problem. I didn't see evidence of a block of ice on the coil, so I would assume the reversing valve was not energized (along with the outdoor unit running). There does not seem to be a problem with the performance of the unit. I get about a 17 degree drop from the return grill to a supply register and the indoor unit with the ductwork is in a VERY hot attic. When the unit is running it does not have a problem cooling the area. It will run fine for 15 or 20 hours before it will mess up. Sometimes it will run longer. I seem to remember a defrost termination stat messing up and causing weird problems with a heat pump once, but that was not intermittent. Whatever this is, killing the control voltage will reset things. I don't work on heat pumps enough to be proficient. Can anyone give me some pointers?