Quadra Fire Mount Vernon (OE) Combustion Fan Fluctuating

[BachJeremiah]

I've got a very early Quadra Fire Mt Vernon stove. It's been working great since I bought it used at the beginning of last season. I scrape and dump the burn pot daily, vacuum the firebox out weekly, and removed the baffles and vacuum the whole stove and heat exchanger area as well as blow the vent pipe out at the beginning of each season and once in the middle. The stove has always ran great until a few days ago. What's happening is about 5 minutes after the call for heat, the combustion fanr speed starts fluctuating. It will slow down to almost nothing, speed back up, drop down, back up, etc. Eventually it will stabilize but might start doing it again that burn cycle or might not until the next cycle. My assumption is that either the combustion fan is going bad (I've had a hunch it's a bit more noisy than it should be since I've owned it) or the control board is bad, outputting inconsistent power to the fan. I'm a mechanic by trade and familiar with general electrical diagnostics, so my first thought was to hook some jumper leads up to the combustion fan (still connected) and then to the multimeter and let the stove start up. If the power fed to the fan is consistent even when the fan is fluctuating in speed there's my answer. My question is if not, should I definitely replace the control board? Figured it was worth asking if this was a common issue or there was some more testing someone could recommend to narrow this down. Thanks in advance, and let me know if there is any other information I can give to assist

 

[Ssyko]

I would test voltage on the motor terminals to see if the board is a lil wacked. If you unplug the stove and then hook up your dmm, plug back in the motor should be on for 12 min then shut off. Make sure your tstat is at the lowest setting. After the 12 min turn tstat up till call for heat and see what the meter says .

 

[BachJeremiah]

Well, while pulling the covers off the stove I spotted a female spade connector that the plastic was melted on. Upon touching it, the terminal it was connected to (a snap disc held on the back of the auger housing held on by a small bracket and a wing nut) fell right out of the snap disc. The manual indicates this is the back burn protector, which can kill power to the whole unit. I'm going to assume this is the cause of my current issue.

 

[BachJeremiah]

The disc has no visible signs of heating up except at the one terminal. Also the internal disc appears damaged which leads me to believe there was a poor connection/high resistance leading to that terminal heating up until the damage to the wire connector happened. I touched it and the male terminal of the snap disc literally fell out. I'm not seeing anything that leads me to believe the disc was damaged due to heat in the auger housing. It also makes sense why it would happen mainly on startup. Based on the wiring diagram it looks like power for the whole unit comes through this disc, so when it was drawing the most juice was in the beginning when the igniter was drawing power as well as the exhaust fan

 

[Ssyko]

Yeah that would cause a big issue. Good catch. I would test the amp draw on the terminals, just to make sure something else isn’t causing the heavy current draw or if it was just a bad switch.