This just happened to me also. The 8 amp fuse was blown in the circuit board on the back of the fridge. (looks like a old car fuse) got a pack at radio shack. I replaced the fuse and it blew again. There are 2 electric heaters wired to the box and are located in the exhaust stack. I had one bad heater and bought one at camping world, I think it was about $50.00 and replaced it my self. To check which heater is bad, unplug 1 heater and put a new fuse in. If it doesn't blow this means the other heater is bad. Plug in the bad heater and the fuse should blow. Remove and replace the bad heater and you should be fine. This is what I did.
2007 Winnebago Tour 40ft