Every once in a while, furnace blower keeps running after turning off after using fan only and only when I use fan only. I thought it was a problem in the thermostat, so I pulled it out of the socket. Fan continued to whir.
I measured the voltage across green and red and read 24V as the fan continued to run, so it's clear that there isn't a short in control wiring.
To shut it off, I'll have to short red and green a few times with a paperclip at the thermostat socket and fan eventually turns off.
If I don't do this, it contiues to run forever. I can also do the same shorting technique to get the blower stuck running. My assumption is that pulsating the control terminals turns it off by jiggling the stuck terminals apart.
Is there anything I should suspect beside the mechanical relay?