While I was troubleshooting the issue with the outdoor unit this afternoon, I realized I had a major problem with my main electrical panel. I had purchased replacement fuses for the outdoor disconnect, and when I tested the system again, the fuses immediately blew again. However, right after that happened, I I heard some noises that you definitely do NOT want to hear coming from your electrical system - basically like electrical arcing or sparking. I immediately ran to the panel and turned off the breaker to the heat pump (the only breaker I had on during the test). It was then that I realized I was in for a whole lot more trouble than I had originally feared.

I decided to start trying to straighten up some and button up whatever I had torn apart at that point so I could start focusing more on a possible electrical issue. Then I went back inside and realized that a bunch of electrical circuits had suddenly stopped working, despite the breakers still being on. Oh crap.

So, I removed the panel cover and started troubleshooting. Bizarrely, I'd get voltage across some breakers, but not others. Then, while I was still looking for the gremlin, things just magically started working normally again. What in the heck? Then I decided to start trying out loads on some of the circuits. When I tested the dryer, it ran, but the main panel immediately started making awful noises again. At this point I was totally in over my head, so I reluctantly called my electrician buddy. My reluctance was only because I knew he would insist on dropping what he was doing and immediately coming over to help me. At this point it was about 6:00 PM. He arrived about 30 minutes later, and we quickly determined that the main breaker was failing and making intermittent contact with one of the bus bars in the panel guts. Clearly the easiest and most cost effective solution would be to replace just the main breaker, but with a 45 year old panel, the odds of finding that breaker were slim to none. So we ended up having to buy a brand new panel and breakers and change out the entire panel tonight. It was a tedious and frustrating process, mainly because the new panel was wider and taller than the existing panel, so we had to modify the size of the framed opening for the panel. Let me tell you - that is a lot of fun to do in a small laundry room working around adjacent appliances and wall cabinets.

We finally finished at about 1:30 AM. Power seems to be all back to normal now, but the HVAC issue still exists. It's looking like maybe the electrical issues could have caused an issue with the outside disconnect, because I'm not getting voltage through the fuses now, despite them still being in tact and having continuity. My brain is fried now though so I'll have to see about that tomorrow.

What a day. Thanks again for everyone's input.