I have a carrier furnace (17 years old) that quit recently. After wiggling a few wires, tapping here and there, I could get it to start up and operate for several days before it quit again. (it has electronic ignition) I can get it to work, but now it works only for one or two cycles (it's getting worse). Sometimes I can get it the pilot to light, then it shuts off. I try again and everything works fine. It seems to be the ignition lockout device (the part where the spark plug wire originates) , but the repair guy replaced that temporarily and it didn't SEEM to be the problem although my method to start the furnace is to wiggle and jerk on the wires coming from this part. So he replaced the main gas valve (for 350 bucks) but the furnace stopped working again the next day. It never does the same thing twice - it seems to be possessed by demons.

Any ideas?

Sounds like you have a defective 2 or 3 wire pilot. I would start by checking/replacing that part.

Sometimes the pilot assembly can get carbon built up and will block the gas flow. If it has a themocouple then try replacing it. Or you may try taking the pilot assembly out and cleanning it with wd40 then blow the excess cleanner out

I recently repaired an identical furnace with identical problems after replacing the pilot burner, it still acted up by intermittant lighting, and then going out. I found that a wire in the harness just above the gas valve, and plugging into the inducer board located behind the pressure switch was the culprit. It was not making contact all of the time, and the flame sensor would lose power and the burners would go out. By removing the harness connection from the inducer board, and lightly sanding with emery cloth the contacts (solder) on the board, the dumb thing started working again. I have actually had to do this twice over the past few years on different furnaces, and maybe it will work for you.

Thanks everyone.

I replaced the ignition / lockout (the part where the spark originates from the coil) and it everything works fine now. This part has some control of nearly everything, so it can shutdown anything other part, so things are spooky when it starts to fail. It was the part IGM33WZ512 on this page...

IGNITION MODULES: Best Buy Heating and Air Conditioning (http://bestbuyheatingandairconditioning.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=IM)

The repair guy replaced this part originally and the thing still wouldn't work.. probably because it was an old part pilfered from one of my neighbor's furnaces and he just happened to have it in his van. It had the same problem... well , because it had same problem. When I replaced it myself with a true new part in the link above, it worked fine.

Meanwhile, I have a $350 gas valve the repair guy installed that I don't really need.:eek: