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21

Code 21 — Gas Heating Lockout

Bryant · Air Conditioning

What does 21 mean?

The system has locked out gas heating operation. The system will use heat pump heating if available.

Common Causes

  • Failure in the gas heating components
  • Control board malfunction
  • Safety switch tripped
  • Gas valve issue

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check if the gas supply to the unit is adequate.

  2. 2

    Inspect for any error codes related to ignition or flame proving.

  3. 3

    Ensure safety switches are not tripped.

  4. 4

    Contact an HVAC technician for gas heating system diagnosis.

Browse all codes in this manual (47)
Verified technical data. Last updated: April 2026

Related Faults

13Code 13 — Limit Circuit Lockout14Code 14 — Ignition Lockout15Code 15 — Blower Motor Lockout
Source: Bryant Air Conditioning
Open Manual (Page 17)Search more codes in this manual