Status code34Carrier
What it means
Ignition proving failure: flame not sensed during trial for ignition. Control tries 3 more times before lockout 14.
Call a profurnace
How it shows: Status LED: 3 short flash(es) then 4 long flash(es) (code 34)
§1Likely causes
- Oxide buildup on flame sensor
- Gas valve defective or turned off, or manual shut-off valve closed
- Low inlet gas pressure
- Inadequate flame carryover or rough ignition
- Defective hot surface igniter
- Control ground continuity problem (green/yellow wire must be connected to furnace sheet metal)
- Flame sensor grounded
§2Safe DIY steps
- Check that the manual gas shut-off valve is open and the gas valve is ON
- Technicianclean flame sensor with fine steel wool and check flame current (0.5 microamp DC minimum, 4.0-6.0 nominal)
- Techniciancheck igniter, gas pressure and ground
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 gas is on and the code persists.
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.
31CarrierLow (LPS) or high (HPS) pressure switch did not close or reopened.