Here's one for the guys who know about HVAC stuff. I have an Econar geothermal heat pump that heats and cools my home. I installed it new in 1989. It has been pretty reliable, but when it was about 10 years old I did have the mechanical controller replaced with a circuit board. When I decided it was cold enough around here to start heating recently I found that the circuit board was dead. None of the lights on it were on. A little bit of snooping around revealed that it has a 2 AG fuse on it that was blown. I replaced the fuse and turned on the circuit breaker. The fan started, about 10 seconds later the fuse blew, before the compressor started. I don't know if the fuse blew when it was attempting to energize the compressor relay, or if it was prior to that. But the compressor relay did not click on. I don't have any more fuses of that size on hand so I'm going to have to get some, but I would like to diagnose the cause of the fuse blowing before I put another one in. Does anyone have any suggestions on what components I should check, and how to check them? Attached is the wiring diagram and pictures of the components. I don't see any chafed wires or anything like that that could be grounding out. Thanks a lot, Joel