The furnace in my Cherokee 39L stopped working, the first day of deer season. It is the F30. It would run about 30 seconds then shut off. I took the furnace out and took it to the dealer to check out. There was a chaffed wire in the bottom of the furnace, where the heat comes out, shorting out and stopping the sparking process and shutting it down. If anyone has a problem with their furnace and is taking it out for repair, you might want to check this wire and isolate it from the metal. I used hi heat gasket silicone. There was also a screw missing from the rear brace on the fan motor, probably causing more vibration than usual. I don't think there was ever a screw in it. Also it is a very poor place to run the wires.