Payne PG8MAA Error Code 31: Pressure Switch Did Not Close or Reopened
What Does Code 31 Mean?
Status code 31 on the Payne PG8MAA comes from the pressure-switch circuit that proves the induced-draft (inducer) is moving combustion gases safely. When the inducer starts, the switch should close to confirm proper draft. Code 31 means it did not close, or it closed and then reopened, so the IFC will not allow the burners to fire.
The control's response depends on which switch is involved. If a low-pressure switch stays open longer than five minutes, the inducer shuts off for 15 minutes before retrying. If a high-pressure switch stays open for one minute after the gas valve closes, and this repeats over three successive trials, the control locks out for three hours before retrying.
This is a venting and draft fault, so it is closely tied to combustion safety. Some causes are homeowner-checkable — a vent pipe blocked by ice, debris, or a nest; a clogged condensate drain that can back up and trip the switch; or excessive wind causing backdraft. Other causes — a defective inducer motor, low inducer voltage, disconnected or obstructed pressure tubing, a defective pressure switch, low inlet gas pressure, or improper vent sizing — require a technician. Note this is the opposite condition from status code 23, where the pressure switch failed to OPEN when expected.
What You'll Notice
- The inducer motor spins up but the burners never light.
- The furnace tries, pauses for several minutes, then tries again, or stops for a longer period.
- It happens more on very windy days or right after a hard freeze.
- The exhaust or intake termination outside is partly blocked or iced over, or the condensate drain is backing up.
Common Causes
How to Fix It: Clear the vent, intake, and condensate drain
What You'll Need
Steps
- Turn off electrical power at the breaker and shut off the gas supply valve before servicing Switch the furnace breaker or power switch to OFF and turn the manual gas shutoff valve to OFF (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
- Inspect the outdoor vent and intake terminations Go outside and check the furnace's exhaust and combustion-air pipes where they exit the house. Clear away snow, ice, leaves, insect or bird nests, or any debris blocking the openings or screens, and make sure the terminations are not buried or pressed against a wall or shrub.
- Check the condensate drain A clogged condensate drain or trap can back up and open the pressure switch. If you can see a blocked or full drain line or trap, clear it and let it drain. Do not disassemble the internal pressure tubing.
- Rule out wind and obvious tubing issues If it is very windy, wait for calmer conditions to see whether the fault clears. Visually confirm the small pressure-switch tubing is not obviously disconnected, but do not attempt to remove or repair it.
- Restore power and gas, then retry Turn the gas and power back on. You can cycle power for about 30 seconds to clear a lockout, then call for heat and watch whether the inducer proves draft and the burners light.
When to Call a Professional
Contact a licensed HVAC technician if:
- Code 31 persists after the vent, intake, and condensate drain are confirmed clear
- The inducer does not run, runs weakly, or sounds like it is failing
- You suspect disconnected or obstructed internal pressure tubing or a failed pressure switch
- The furnace repeatedly locks out for three hours, or the vent may be improperly sized
Frequently Asked Questions
What is the pressure switch checking on my Payne furnace?
It confirms the inducer is producing enough draft to vent combustion gases safely. If it can't confirm that, code 31 blocks ignition to keep exhaust from spilling.
Could a clogged drain really stop my furnace?
Yes. On this design a backed-up condensate drain can open the pressure switch and trigger code 31, so clearing the drain is worth checking before calling for service.
Sources
✓ Verified against manufacturer service manual — March 2026