Payne furnace: Code 21 — Gas Heating Lockout (No Auto-Reset)
Professional repair
Payne furnaces share the Carrier control platform — this code table applies to the equivalent Payne models. Confirm against your unit's panel label.
What does code 21 mean on a Carrier furnace? Official: mis-wired gas valve, a stuck-closed gas-valve relay on the control, or a shorted gas-valve wire. This one does NOT auto-reset.
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.
Gas-side control fault — licensed tech only. DIY part cost: $120–250 — a pro visit for this class of fault typically runs $150–350.
What causes it (in order of likelihood)
- Control board gas-valve relay stuck TECH
- Gas-valve wiring error/short 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 series · Payne PG8M series
Different Payne 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.37/48
Last verified 2026-07-06 · how we verify