Carrier furnace code 31: Pressure Switch Did Not Close or Reopened
Try DIY first, then call a pro
What does 3 short 1 long flashes mean on a Carrier furnace? If the switch stays open over 5 minutes, the inducer rests 15 minutes and retries. Official checklist: excessive wind, low inlet gas pressure (if LGPS used), disconnected or obstructed pressure tubing, defective switch.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Homeowner checks for Carrier furnace code 31
This is a limited outdoor observation check, not a complete furnace repair. If you smell gas or a carbon monoxide alarm sounds, leave the home right away without operating any switches, then call the gas utility or 911 from outside. Never bypass a safety switch or reset the furnace over and over.
- Turn the furnace off
Turn off the furnace at the thermostat and its nearby power switch before checking the vent ends. Keep the furnace cabinet closed.
- Find the vent ends from ground level
Locate the furnace intake and exhaust pipe ends where they leave the house. Only check ends you can see and reach while standing on the ground. Do not climb a ladder or go onto the roof.
- Clear loose snow or leaves by hand
If it is safe to stand there, brush away loose surface snow or leaves from around the openings by hand, without tools. Do not reach into the pipes, chip at ice, or remove or modify any pipe, cap, or screen.
- Stop and call if anything else is wrong
Leave the furnace off and call a technician if you find ice, a nest, a damaged pipe, or anything you cannot clear safely by hand. After clearing only loose surface snow or leaves, restore power and observe one heating cycle. If the code returns, turn the furnace off and arrange service.
Switch and inducer testing. DIY part cost: $30–60 — a pro visit for this class of fault typically runs $150–350.
What causes it (in order of likelihood)
- Blocked/disconnected tubing, wind-affected venting DIY-CHECKABLE
- Defective pressure switch TECH
Parts referenced by this code
Always match parts against your model's parts list — part numbers vary within a series.
Questions about this code
What does 3 short 1 long flashes mean on a Carrier furnace?
If the switch stays open over 5 minutes, the inducer rests 15 minutes and retries. Official checklist: excessive wind, low inlet gas pressure (if LGPS used), disconnected or obstructed pressure tubing, defective switch.
How do I fix Carrier furnace code 31?
From ground level, check the outdoor intake and exhaust ends and clear loose snow or leaves by hand if safe. Strong wind can also play a role. Tubing, gas pressure, and switch testing need a technician.
How much does it cost to fix Carrier furnace code 31?
If a blocked vent end was the cause, clearing it may be enough. Otherwise cost depends on whether tubing, gas pressure, or the switch is responsible.
Related symptoms
These symptoms can appear alongside this code. The link is an association, not a diagnosis, and code meanings vary by brand, model and control.
Applies to
58STA · 58STX
Different Carrier generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Same control platform, same code: Bryant furnace code 31 · Payne furnace code 31
Verified against Carrier 58STA/58STX Installation & Service Instructions (1106202L), p.37/48
Last verified 2026-07-06 · page updated 2026-10-07 · how we verify
Related Carrier furnace codes
These codes use the same status led — short + long flash codes system.