Bryant furnace: Code 34 — Ignition Proving Failure
DIY-friendly fix
Bryant furnaces share the Carrier control platform — this code table applies to the equivalent Bryant models. Confirm against your unit's panel label.
What does code 34 mean on a Carrier furnace? No flame proved during the trial for ignition; the control retries 3 more times before lockout 14. Official checklist: flame sensor must not be grounded, oxide buildup (clean with fine steel wool), proper microamps (0.5 min, 4.0–6.0 nominal), gas valve on, igniter health, inlet gas pressure.
This condition involves the gas or combustion side. If you smell gas or a CO alarm sounds: leave, then call your gas utility. Diagnostic info here is reference — combustion repairs are for licensed technicians.
GOOD NEWS: THE FIRST CHECKS ARE FREE AND TAKE MINUTES.
Try these first — in this order
Clean sensor, confirm the igniter glows, check the gas valve is on — 20 minutes.
Pressure adjustment and valve replacement. DIY part cost: $8–18 / $20–40 — a pro visit for this class of fault typically runs $150–350.
What causes it (in order of likelihood)
- Oxidized flame sensor — clean with fine steel wool (official) DIY-CHECKABLE
- Defective hot-surface igniter (should glow orange-white in 15 s) DIY-CHECKABLE
- Gas valve off/defective, low inlet pressure TECH
Parts referenced by this code
Always match parts against your model's parts list — part numbers vary within a series.
Applies to
58STA · 58STX · Bryant 310/311/312 系 · Payne PG8M 系
Different Bryant generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Carrier 58STA/58STX Installation & Service Instructions (1106202L), p.37/49
Last verified 2026-07-06 · how we verify