I have run into a problem that has me puzzled. Maybe someone can help. This unit was running just fine before this couple went on vacation for two weeks when they returned the unit would not run .
the unit is blowing fuses, I checked control wiring at hp unit, t-stat, and connections at the furnace there's no damaged wires, there is no visual(front or back) damage to control board.....so I completely disconnected control wiring from furnace replaced fuse, turned on power and it blew fuse, so I checked voltage at transformer 26.9v. There is only 2 components in the furnace control board and the transformer. Is the control voltage to high or is the board bad?????