I have a Trane TUD080C936J0 gas furnace/ac. The furnace starts up via a hot surface ignitor.
The ignitor that was in it went bad, and I bought a replacement. When I plugged it in, it worked fine - once. The next time it called for heat there was a pop and a tinkling sound and the ignitor was in pieces - it looked like thermal shock or something.
I took that back and got an exchange, but the one they gave me was pre-cracked, and as neither of us checked it out at the store they wouldn't give me an exchange.
A couple of weeks later, a new one came in from an eBay seller. This one has about 40-50 ohms resistance, but the furnace still flashes "check hot surface ignitor. I've plugged my multimeter into the plug that goes to the ignitor and when the thermostat calls for heat it spikes for a moment (I typically see 500/1500/200v flash) and then it goes back to zero. I even plugged my multimeter in series with the ignitor and got the same behavior, but still no dice. Is it possible I just got another faulty ignitor? Is there a way that I can test the ignitor, like just plugging it into a wall socket or something? Presumably not while actually holding it, of course.
The furnace did flash one of the other trouble codes at first, but that switch was apparently just a little stuck - pulling it out and warming it up let it reset, and it doesn't flash that code anymore.