We just got back home, and our thermostat was off and the house chilly. I’m still getting 28vac on red and blue, and the heater controller seems to have power. I installed a dumb thermostat to make sure it wasn’t my smart one, and no change.
Unit is a Trane XR80, and the controller is a White Rodgers Intell-Ignition 50A65-475.
Any suggestions, or is this a service call? If it’s a service call, any recommendations for an honest company?
Gas, electric or heat pump?
Gas, but I got it figured out…
Fuse on the control board was blown, but the board was still showing power. Quick trip to ace and back in business
Mine has several interlocks, one being a pressure switch on a powered flue. Sometimes it sticks and will not start the furnace until it is blown out.
Glad you got it sorted! We had that fun 2 years ago on Christmas Day. Heat went off at 6:30 pm and none of the stores that were open carried the fuse we needed! Stupid rat/squirrel had chewed the wire outside on the condenser unit and shorted it. Check the wires, that fuse doesn’t just blow by itself. And have some spare fuses taped to the side of the furnace 
Soooooo…The interesting thing to me is why did the fuse blow? If you just hooked up the smart thermostat then i get it. People blow them all the time on the install. If not then you have something else going on.
Also…PLEASE tell me you weren’t a jack hole and put in a higher amperage fuse to keep it from blowing. The ONLY time that is permissible is to observe the high current draw component.
I pulled a 30A fuse off a board a week a two ago, they are usually 3 or 5A, depending on mfg. The home owner had no idea and that is definitely a fire hazard. In that case the gas valve was misbehaving and blowing the fuse. I replaced the gas valve and moved on with life.
I was worried about something like this as I’m very unfamiliar with a/c systems. Of course, the installer apparently used duct tape to lock the door switch closed. So, yeah, you could totally start up this system with the cover off the controller
@jswilson64 @Tres0422 it looks like we may have had a power surge while we were gone. Microwave clock etc all reset. And don’t worry, 5a fuse blown, new 5a put back in 
