I get to wake up on New Year's Eve to a furnace that clicks but doens't heat. Yum! I hope ya'll can help.
It's a Bryant forced-air natural gas unit, model 394GAW036075.
Even when the thermostat is set to OFF the pilot ignitor still fires away, about twice per second. If the thermostat is set high enough to call for heat then the sparks get faster (about 3 or 4 per second) but the pilot does not light.
I turned off the power, cleaned the ignitor with compressed air, and checked the wires for good connection with no change. No sign of shorting.
At first, that seemed to work as the ignitor started working normally. I put the cover back on and it was back to clicking. I started to take off the cover and in the process banged near the black box that seem to power the ignitor spark and it started working again, but only for a cycle or two and now it isn't working at all.
Disconnecting the thick orange lead from the ignitor make the sparking stop (of course), but there is still a clicking noise from the black box.
So how do I figure out if it's the black ignitor box or upstream of it?
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.