I've had an intermittent problem with my Bryant 350MAV for a couple of years. The motor will kick on but then it will just run. After a while I realize that it's getting cold in the house, the motor s running but I never heard the whoosh of the gas igniting. I pull the panel and see that it's flashing error code 21. I had the techs out several times and they just wiggled the wires and told me it was fixed. The last few times it has happened I just turned off the furnace and wiggled the wires myself and when I turned it back on the LED would be a steady glow and it would generally work for 3 more months or so before it failed again. But this time that didn't work. I've turned it off at the thermostat, turned it off at the switch on the furnace and cycled through that several times. It is totally ignoring any command sent from the thermostat, and when I turn off the switch at the furnace and wait a while then turn it on it immediately flashes code 21 and the motor just runs. My comfort level stops at wire wiggling, so I'm just wondering what to tell the tech when he tells me that the circuit board is bad and needs to be replaced for hundreds of dollars.