Furnace fan won't turn on

I just tried it again out of curiosity, and, you guessed it, it came right on. I suppose it's going to work perfectly until late September when I'll be fishing up some remote high elevation Forest Service road and it will puke again. 

You can Google up the service manual which has a troubleshooting chart. But the troubleshooting protocol is to get out your trusty multimeter and check the stat, fuses, switch, etc to be sure you're getting 12V to the blower time delay relay. You can just jumper around the tstat if you want to for test purposes.

If you are getting 12V to the time delay relay but the TDR isn't closing to provide 12V to the blower then replace it. Otherwise the problem would have to be the blower motor itself.

Good luck and please let us know what the problem and fix were.