furnace fuse blowing

budwich wrote:
I guess you "own the problem"... :-)
disconnect the power wires going to the furnace, plug in a new fuse, does it blow? No? then its not the wiring going to the unit. Yes, then its the wiring going to the unit. Since you are the one that has been "playing" in the unit, it is likely that "playing" may have introduced the problem, such as miswiring, shorted connection / chafed wiring. Further, disconnect all wiring going to the control board except the power leads (ie. 12v and ground), does the fuse blow? If not, then your issue is with the "stuff" coming into the board. If yes, then your problem is with the board.

One other thing, you refer to "the unit" but exactly what are you "playing with"... the control board, the motor, the thermostat? what wiring are you actually disconnecting / connecting?

I don't mean to be difficult here.

The unit as I refer to it is the furnace assembly, all I have done to it has been pull it out of the camper by disconnect the wiring and gas line. I have taken it to the dealer for repairs in the past, 2 years ago was the latest, a blower motor was replaced. That is spinning freely.

I have the furnace at home and wanted to put power to it with an inline fuse as a bench test.
good idea checking to see if the fuse blows with unit wires disconnected.

thanks,
Jim