Bryant · Furnace / HVAC
31 Pressure switch fault (venting/draft)
What this code means
The furnace's pressure switch failed to close, or reopened mid-cycle, so the control board stopped the burners. This safety switch confirms the draft inducer is actually pulling exhaust through the flue before gas is allowed to flow — it isn't a false flame reading.
Most likely causes
- Blocked or restricted flue/vent termination
- Failing draft inducer motor
- Clogged condensate drain line or trap (condensing furnaces)
- Disconnected or pinched pressure switch tubing
What to try first
Check the outside vent termination for blockage (snow, leaves, nests) and make sure the condensate drain isn't clogged or frozen. Don't bypass the switch to force the furnace to run.
Safety note: if this code returns after one clean reset, stop resetting it — repeated lockouts usually mean a real fault that needs a licensed technician. Never bypass a safety switch.
FAQ
What does Bryant error code 31 mean?
Pressure switch fault (venting/draft). The furnace's pressure switch failed to close, or reopened mid-cycle, so the control board stopped the burners. This safety switch confirms the draft inducer is actually pulling exhaust through the flue before gas is allowed to flow — it isn't a false flame reading.
Can I fix Bryant code 31 myself?
Usually not. Check the outside vent termination for blockage (snow, leaves, nests) and make sure the condensate drain isn't clogged or frozen. Don't bypass the switch to force the furnace to run. If the code returns after one reset, it needs a licensed technician.
What causes Bryant code 31?
The most common causes are: blocked or restricted flue/vent termination; failing draft inducer motor; clogged condensate drain line or trap (condensing furnaces); disconnected or pinched pressure switch tubing.
Other furnace brands: Trane · Carrier · Lennox · Goodman · Amana · American Standard · Rheem · Generic · Nest
This information may contain errors or not apply to your exact model — always double-check it against your appliance's own manual before acting. If there's any chance of a gas, fire, electrical, carbon monoxide, or other safety hazard, stop and call a licensed professional or the appropriate agency (e.g. your gas utility) instead of relying on this page alone.