Bryant furnace won't stop clicking
OK, problem seems to be resolved, but I don't quite understand what was going on.
I noticed that the clicking/arcing stopped when the thermostat was disconnected. Hmmm. Maybe bad thermostat?
But wait a sec, even though sparky was zapping away, the gas didn't actually come on for the pilot, no matter where the thermostat was. What if I jumper out the thermostat? Still the same; sparks but no gas.
OK, sparks but no gas usually means bad valve, right? So I checked the valve and, yep, it was bad. It was getting voltage but not letting the pilot gas through. I couldn't find one I could buy (New Year's Eve; most shops closing early, many not willing to sell to a DIY'er), so I called a tech. He brought a new one over and put it in. $259 *sigh*
Everything works just fine now. The tech could not tell me why the sparking would have been caused by the bad valve, even when the thermostat was set to OFF. Perhaps there was some odd short inside the valve.