I just moved into my new home and have a 1991 Comfortmaker RPJII natural gas furnace model GUI075A012IN, the AC is a 1999 Trane. Up until this issue, everything has worked flawlessly. The other day I was flipping breakers trying to figure out what they all went to. I then flipped off the one that goes to my HVAC. I flipped it on and off a couple of times and then after I flipped the breaker back on the final time, nothing would cycle back on. I also smelled a very distinct electrical burning smell. Neither the furnace, blower or ac would go on. I set the thermostat to "On" to try to force the blower to go on. I cranked the temp up and then down... nothing would work. Upon further inspection, the main 15 amp time delay fuse was blown. Not just melted, black and blown. I replaced the fuse, flipped the breaker on the panel back on and then set the thermostat. Still nothing... so I checked the fuse again and once again it had blown. I then did another experiment. I flipped the breaker to the HVAC off and the power switch on the furnace to off, and set the thermostat to fan only so that the AC or furnace would not power on. That way only the blower would try to turn on. I then put a new 15 amp time delay fuse in, flipped the breaker on and flipped the switch on the furnace to on. IMMEDIATELY after the switched was turn to on, the new fuse blew rather violently. So what do you all think is going on here? Blower motor burned up and that's what I was smelling? Why would me flipping the breakers on and off multiple times do this? Any other ideas? How else can I troubleshoot this?

THANKS!