Nothing working on heat pump or A/C - fan not going either. Just had new thermostat installed. Same thing happened two weeks ago. We left thermostat off - A/C guy came over and flipped the thermostat switch on and it worked fine! Now - same thing - woke up to 64 degrees in house and thermostat set at 70. Nothing happens when I set fan to manual either. Tried throwing the main power off and back on - waited 30 minutes - then flipped the thermostat back on... nothing. Don't know much about this but neighbor thinks it's a bad "relay switch"?

I tend to agree with your neighbor. Get out your multitester and see if it is bad or not. I keep my home here in Ohio at a balmy 62 degrees in winter all the time so I can wear sweaters and use my heating blanket.