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

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Originally Posted by taftsj

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

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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.