Thank you for the help! It looks like the switch is bad, so I've ordered a new one.

I can use a multimeter, yes.

Hi, I just bought a house with an Intertherm CMF2 80 PO CONV. I fired it up for the first time today, and the fan doesn't turn on automatically when the furnace is heating. The fan will run when the switch is on. How hot does the furnace need to get before the fan is supposed to come on? I tried let...