I just had my first couple of nights sleeping in the 16' with the furnace on. When it starts up, it runs with a fairly loud, but smooth "whoooosh" sound. But then it develops a sharp, tinny rattle, almost a screech. This is clearly in the fan.
Has anyone worked on a similar problem? How hard is it to get the fan?
Thanks,
I'll follow up this post myself.
After a while, I just started in, and it was easier than I feared. In my 16' the gas connection is right near the opening to the interior. It was a matter of removing two screws that secure the furnace to the frame, unfastening the flare fitting for the gas supply (all electricity and gas turned off, of course!). Then the furnace could slide out a few inches, and I could reach underneath and disconnect four wires. Then the furnace just slides out, and I took it into the shop for further investigation.
The fan motor is toward the back/outside. It has a squirrel cage on the back that drives the exhaust, and a small four-blade fan on the front end for intake. I removed the outer side of the exhaust chamber - several screws around the perimeter. Inside there was a considerable number of flies. Many of them were alive, but torpid. I presume they went it seeking warmth after the last time I ran the furnace in late October. Then I could remove two 3/8" lock nuts and two more sheet metal screws, reach in a pull out the quick-connect wires, and the inside of the exhaust chamber came out with the motor attached. I found what seemed to be a little turning resistance, so I dribbled a little 3-in-1 oil in the back motor bearing, gave it a few turns, and it seemed to loosen up. I wanted to get at the front bearing, but to do that, I'd have to remove the little squirrel cage on the exhaust side, and it was quite frozen in place. After soaking the shaft with bolt loosener for about 48 hours, I abandoned the effort. I jury-rigged an electrical hookup so I could run the fan off my pickup battery, and it seemed nice and "quiet" (recognizing that's a relative term, but it was a lot better than it had been).
On the reinstall, I made two changes. First, I put a 4-pin connector inline to make it easier to deal with the electrical supply if I ever have to take it out again. Second, I cut two small circles of metal screen material and screwed them onto the outside vents to discourage insects from coming in.
Reinstalled, hooked everything up, and it runs fine, with a normal "whooosh" type of sound.
Randy in Paonia