Burner lights briefly then shuts off; display shows Code 12 (flame failure during operation)

Safety first: Turn OFF gas and power. Do not continue to reset the unit if flame failure recurs; this may indicate a combustion problem.

Steps to check:

• Check gas supply stability: Observe whether other gas appliances dim or fluctuate. If multiple appliances show issues, contact your gas supplier.
• Clean flame rod and burner: Remove the front cover. Carefully remove the flame rod and clean it with fine abrasive pad. Brush dust and debris from the burner surface and vacuum loose material.
• Inspect venting and intake: Ensure intake and exhaust are clear and vent piping is intact without sags or disconnections.
• Reset and test: Restore gas and power, reset the unit, and run hot water. Monitor for stable operation.

When to call a professional: Persistent Code 12 may require gas pressure testing, combustion analysis, or replacement of the flame rod or control board by a qualified technician.