Status code31Carrier
What it means
Low (LPS) or high (HPS) pressure switch did not close or reopened.
Call a profurnace
How it shows: Status LED: 3 short flash(es) then 1 long flash(es) (code 31)
§1Likely causes
- Excessive wind
- Restricted vent or improper vent sizing
- Defective inducer motor or low inducer voltage
- Defective or miswired pressure switch
- Inadequate combustion air supply
- Disconnected or obstructed pressure tubing
- Restricted or blocked condensate drainage, or water in sagging vent pipe
- Low inlet gas pressure (if LGPS used)
§2Safe DIY steps
- Check that outdoor vent and intake terminations are clear
- Techniciancheck vent sizing, inducer, pressure switches and tubing
- Techniciancheck condensate drain and vent pipe slope
Safety firstIf you smell gas, do not touch any electrical switch or use a phone in the building; leave immediately and call your gas supplier from outside. Turn off electrical power at the furnace switch or breaker before opening any panel, and never bypass or jumper a limit, rollout or pressure switch. Gas valve, burner, venting, wiring and control-board work should be done by a licensed HVAC technician.
§3When to call a pro
Call a licensed HVAC technician: if vent terminations are clear and the code repeats.
Find a local HVAC pro →§4Other Carrier codes
13Carrier
Limit circuit lockout: a limit or flame rollout switch was open longer than 3 minutes. Control auto-resets after 3 hours (see code 33).
14CarrierIgnition lockout: system failed to ignite gas and prove flame in 4 attempts. Control auto-resets after 3 hours (see code 34).
21CarrierGas heating lockout. Control will NOT auto-reset.
22CarrierAbnormal flame-proving signal: flame is proved while the gas valve is de-energized. Inducer runs until the fault is cleared.
23CarrierPressure switch did not open.
24CarrierSecondary voltage (24 V) fuse is open.