I have a Bryant 350MAV036080 furnace which sometimes gives me a 31 code on the LED. It will run fine for a few cycles then I'll hear the thermostat click for heat and the furnace won't run. I'll check the code and lo and behold, it's 31. If I leave it alone for about 15 min, it'll kick back on and run fine for a few more cycles.

I've tried everything: cleaned the condensate trap and the hoses which lead to it, replaced the pressure switch, tested the condensate pump, replaced part of the vent PVC and I still can't get the unit to work 100% of the time. The vent PVC APPEARS to be clear outside. I live in a condo where it's hard to get to the actual pipe. I'm beginning to think it's the control board, does this sound like a symptom of a faulty board? Am I missing something else I should try? Thanks.

I had a 31 code on my Bryant plus 90 - repair guy found air switch not closing- ventor would not run. He put in conversion kit #325878-751 - now works fine!

John in Stratford ON

I had a 31 code on my Bryant plus 90 - repair guy found air switch not closing- ventor would not run. He put in conversion kit #325878-751 - now works fine!

John in Stratford ON

Thanks. Was your furnace intermittent with code 31 or was it always not working?

It was intermittent at first and then it quit altogether.

Okay, some success (I think). I took the cover off to the blower compartment where the circuit board is, and taped the kill switch down so it would run w/o the cover. After the thermostat clicked on for heat and nothing happened, I wiggled the wiring harness which connects the pressure switch to the circuit board - started right up. I think this is my problem. Now, is it the harness or the circuit board which is bad?

Remove and replace the wire and connector a few times it might be corrosion

I don't know. My work order says "changed out integrated Bd." So I guess it was the board.

John

I'll bet it is the pressure switch. Try this: next time the LED is displaying 31, nudge the wires where they connect to the p/s. If LED becomes steady, the switch is bad.

Thanks. I've already replaced the pressure switch, and messed with the wires. I think it's fine.