I came home to my furnace having no power even to show trouble codes. I turned off my breaker opened the blower door and it had a blown 5 amp fuse on the curcuit board. I replaced the fuse turned the breaker back to on put the door back on and the furnace and ac kicked back on. After a couple minutes I noticed it was back off. I went back out checked the fuse again. The fuse was fine. I went outside to try to find a short in my wires did not find anything. The furnace again has no power. The breaker is on, I have no external switch, the fuse is ok, and the blower door is back on. Also i used a multimeter to make sure I was getting the 120v to the furnace and it did. Does anyone know what else could have gone wrong?