I've looked around but there's a lot to search for and I can't seem to find my issue just yet so figured I'd ask.
My blower only runs on High and one day during the winter of last year, I had smoke in the cab and the HVAC wasn't working at all. I did not think to check the fuse for the blower under the hood, because the smoke was in the cab and not coming from under the hood.
So what I've done so far recently, this is months if not a year after the smoke and blower stopped working, is replaced the resistor, since I found that it was a common issue for the blower only working on High. After I replaced it, the blower would then only work on the two settings between Low and High, but wouldn't work on Low or High. But that lasted for like a day and I had replaced the Relay and the entire blower+fan itself.
I finally checked the fuse under the hood, it was bad, but when I replaced the fuse and it was a 50A fuse, the blower started working again but only on High.
I got a new switch coming, which is probably unnecessary now but either way, I don't understand what the issue is.
To summarize
1. Would only work in High until something burnt up and it stopped.
2. Replaced the resistor and it started to work on two settings between Low and High but not work on either of those two.
3. It then stopped working all together again. Fuse was burnt out, replaced it and now it only works on High again.
I may have forgotten to remove the fuse before replacing the old blower with the new one, but I am certain that I had pretty much everything disconnected at the time. It also looked like it's been replaced before but I'm uncertain.