| A circuit board failure of the kind you describe is almost certainly a defect on the board, rather than being caused by something external to the board that will recur again.
I've replaced many such boards and never had that kind of repeat issue. No guarantees on that, of course.
Hard to say about the voltage readings you report. I'm supposing you disconnected the inducer motor using the wiring clip connector, and mesured the voltage on the pins going back to the circuit board.
With the thermostat off and the furnace sitting idle, I'd normally expect no significant voltage on either pin. It might be a defect caused by the bad relay or burned circuit board, but that's just a guess.
One diagnostic approach is to consider circuit boards and such to be "black boxes." If the black box doesn't do what it's supposed to do, you don't try to analyze why, you replace the black box.
I think you have a black box there! |