Furnace blowing fuses

[hlozano]

It's that time of year when we go on our first outing for the year. Took the cover off our Reflection 317RST and started going through my normal checks. Since it still gets down in the 30's here in Ohio this time of year, the furnace is one of the first things I check. After bleeding the LP which consists of firing up the stove and leaving it on for a couple minutes, I proceeded to kick on the furnace. The furnace started it's pre-purge cycle then nothing. It never gets to a point where the igniter tries to ignite. It turns out I blew the 15A fuse, so I replace it and try again. Same thing, blown fuse. I checked to make sure I wasn't getting continuity to ground at the fuse connection which tells me the circuit isn't shorted. It can't be the reset switch because I'm reading 12volts with a good fuse. So I'm thinking control board since I had problems with it last year. (I had a problem with the control board last year. I basically had to solder a new jumper because of Atwoods poor design and placement which allowed the control board to sit in water.)

I ordered a new control board from Amazon and installed it, fingers crossed, turn on the heat and same thing, blown fuse. Now I'm scratching my head! I decide to throw in a 35A fuse just to see if the furnace would fire. To my surprise the furnace fired right up. I only let it run for a couple minutes then shut if off because I didn't want to damage anything with the larger fuse. I then put a 15A fuse back in and turned the furnace back on and again it fired right up. I set the thermostat to 68 and continued to let it run waiting for it to cycle off. After about 20 minutes it was getting pretty toasty in the coach yet the furnace continued to run. I grabbed my temp gun and pointed it at the thermostat and got a reading of 71 degrees. I ended up lowering the temp setting on the thermostat down to 64 before the furnace finally cycled off.

My theory on the blown fuses is the blower may have been seized a little from sitting all winter causing a higher start up amp draw. Someone please chime in if I'm wrong in my though process. As for the furnace not cycling off, my wife swears in the past she's shedding down to a T-shirt before the furnace finally kicks off. Is there anything I can do to calibrate the thermostat is that just the norm?

[Buckaroo]

You could be right about the fuse blowing due to a stuck fan. Not sure if you have a capacitor on that blower motor to start it but, if so, that could be another potential cause - the capacitance might be on the edge so you didn't have enough oomph to get it over the hump and rotating. If that is the case, at some point it will likely get worse to the point that it won't start at all. Also, the thermostat might be operating normally. There is always a range between shut-off and start with the setpoint somewhere in between. Check the specs on the thermostat.