Bryant Furnace 21 Error Code — Meaning & Repair Cost (2026)
Gas heating lockout — the main gas valve relay on the furnace control is stuck closed, or the gas valve wiring is mis-wired or shorted. The control will not auto-reset. Below: the most likely causes, and what the matching repair costs — Estimated national ranges with a metro localizer. Reviewed July 2026.
What 21 means
Gas heating lockout — the main gas valve relay on the furnace control is stuck closed, or the gas valve wiring is mis-wired or shorted. The control will not auto-reset.
Likely causes, most common first
- Main gas valve relay welded closed on the control board
- Mis-wired or shorted gas valve wiring
- Failed furnace control board
Base: 1 published national repair-cost guide (retrieved 2026-07) · full source registry on the methodology page · Code meaning & causes · Reviewed July 2026
What it usually costs to fix Estimated
21 on a Bryant furnace resolves to the gas furnace gas valve replacement problem. Bryant is priced at the mainstream parts baseline — no brand adjustment applies.
$300–$800 national estimate to fix the fault behind 21. Enter a ZIP to localize.
| Most common repair | Typical total | DIY? |
|---|---|---|
| Gas valve replacement (standard single-stage) | $300–$650 | Pro recommended |
| Gas valve replacement (multi-stage / modulating, high-end) | $450–$800 | Pro recommended |
Plus a typical service-call / diagnostic fee of $75–$150, often credited toward the repair.
Pick a quality tier for a class-typical estimate, or a specific brand to override it (brand adjusts the parts portion only). Enter a ZIP or Canadian postal code to localize to your metro's labor costs. Everything updates without a page reload; no data leaves your browser except the shard lookup.
Base: 2 published national repair-cost guides (retrieved 2026-07) · full source registry on the methodology page · National base range (BLS OEWS May 2025 + BEA RPP 2024) · Reviewed July 2026 · Estimated
Codes are universal — your location changes the repair price, never the code's meaning. See the methodology for the exact localization formula and sources.
Reviewed by a Red Seal–certified appliance technician who also holds a Technical Safety BC gas ticket (Gas-C) and an ODS/halocarbon refrigerant ticket (CFC/HCFC/HFC).