Well, I'm facing a new conundrum, the blower on my furnace has started to have random speed fluctuations when it cycles as of late.
My Camper's furnace is a Suburban DD17DSI direct-discharge furnace, it was installed as a replacement unit by the camper's previous owner for the giant Duotherm it originally came with.
The symptoms are randomly the motor will act like the voltage has dropped or been cut to it, then come back up to normal, or come back up and keep running but fractionally slower.
I'm pretty certain it's not the sail switch, as that failing would simply prevent the furnace from lighting.
Is this the most obvious and just a dying blower motor or is it possible the circuit board that drives the furnace is on it's way out?
To a point, I kinda hope it's the circuit board, as I can service that without completely removing the furnace, to replace the blower will require pulling the furnace and disassembling it to replace the blower motor.
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I had a camper years ago that kept having the same problem. I would say check two things--
Replace the relay that supplies power to the motor, the contacts may have worn out or have arcing scars. You could also just take a fine grit file or course sandpaper to clean the relay.
The other thing that it could be is the brushes gone bad in the motor.
Thanks Boaty, this furnace has seen four years worth of full-timing use as the heating source for the camper. I'll see about snagging a new relay for the furnace, though given it's location, I may simply replace the motor as well because I'll have to extract the unit to access the relay.
Alright, a little research has revealed that in all instances, the furnace will need to be completely removed to service it, I forgot about the shield on the side of the unit over the control card.
I have found a source for a new blower and the service manual, still hunting for a source for a replacement relay (Part #231769). The unit uses what it's marked as a time delay relay that the blower motor is connected to.
Between Boaty and the Service manual, I've sadly completely removed the control board from the equation, as it has nothing to do with the actuation of the fan motor itself, that is solely turned on and off by 12 volt feed coming from the thermostat to energize the relay.
Before ordering a new motor - do this. Locate a 12v and ground, and run a jumper wire directly to the motor. If the motor stays running normally, you know it's not the culprit and it's likely the relay.
Also check the connections for corrosion, specifically any kind of removable connectors, like spades and plugs. Pull them apart and put them back together several times to work any corrosion off of them.
Da**, I absolutely hate it when you can't disassemble something to inspect it or repair it.
This particular furnace model was built to be relatively easy to replace parts on, but rebuilding the parts is unfortunately not possible.
If it weren't for a $500+ price tag, I'd be tempted to just upgrade to one of their quieter newer direct discharge furnaces that have the optional ducting connection so I could route an extra vent up to nearer the cabover entrance.