Sure's chilly when the furnace isn't working

Winter weather has come to Colorado and my gas furnace is acting funny. It works about half the time. It's a Janitrol and uses a surface ignitor. The ignitor works fine, burners light for 10 seconds or so and then go out. It cycles over and over and then shuts down. However, about half the time the burners will eventually stay on and it works fine until the thermostat turns it off.

I figured it was the flame sensor, so I cleaned it, and that didn't work. So I bought a new one, and that didn't work either. That's about all I know to do in this situation. I've seen people talk about a grounded board, or replacing the board, but I'm not sure I understand that option.

Also, the light usually blinks once when the furnace doesn't work, which is flame sensor or gas flow. I'm pretty sure the gas flow is fine. Once, I saw it blinking five times, which is stick valve. Not sure what the deal with that was.

Anyone got thoughts about this?

 

There could be a mechanical problem with the gas valve which gave you the stuck valve trouble code. The valve not opening all the way would also prevent the burners from lighting until after a few attempts when enough gas had built up.

 

Something is turning off the burners.

When the burners turn off, does the inducer motor shut off as part of the cycle?

Also, I'd use an AC voltmeter to check and see if the pressure switch is opening, which would shut off the furnace.

 

I'll check these items. I think the inducer motor stays on during the cycle, but I'll double check. I'll post later with the news. Thanks.