Anyone got an idea on this odd furnace fan noise?
It sounds like something rubbing the squirrel cage fan, but only when it's cold. When I fired it up for the first time this year it just howled and howled, a steady noise. When I realized it wasn't lighting and turned the propane on, ahem, it fired as normal once the propane started feeding. As it warmed up the noise got lower and lower in volume until it cycled off. Then when it cycled back on the noise was still there, just very muted and it finally faded completely. Thereafter that evening it sounded like normal. I remember it did this some last year but never realized it was directly temperature related.
When I first bought the coach the fan would run but it wouldn't light. After some troubleshooting and cleaning of various insect evidence I found the sail switch to be stuck off. After freeing it up I figured I'd try it and see if I needed to replace the switch or not. It fired but made the noise. My first thought was either my insect nest cleaning was inadequate or I had mucked up the sail switch so I opened it back up. Neither was an issue that I could tell. I could see no way the sail switch would actually contact the fan and it worked fine. Finding that the noise went away I skipped it.
Not a huge deal since it goes away but it still bugs me. What is it? It's been a ways back so maybe it was too warm for the issue when I took it apart? I have some other issues that should be looking at but this bugs me and I'm wondering if I need to crack it open again when it's cold for another look.
It would be nice if someone had seen this before and could save me doing more exploratory surgery. I can hope, right?