My heat pump had been running for approx 2 weeks, when I arrived home one evening to find that it was cold in the house. The thermostat display was off (no batteries in this one). Thermostat replaced and heat pump still not working. Fuse was blown. Once fuse was replaced, heat came on and ran for at least 30 minutes as normal. I left home, so I'm not sure when it went off again, but I returned 24 hours later and it was cold in the house. The fuse was blown again. Now the outside heat pump until fan will not even come on, but the emergency heat does produce warm air from the vents inside. What should I look at next as the most logical problem... or what order shoujld I troubleshoot things?

I would say your defrost board on the outside unit has a short, heat works good till it goes to defrost then blows the fuse.