12
Noritz
Flame Loss During Operation
Boiler ignites briefly then shuts down; display shows error 12 and burner goes out.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Unstable gas pressure, Dirty flame rod, Poor combustion air supply, Blocked exhaust or flue
How to Fix / Troubleshooting
Safety warning: Turn OFF power and gas before opening the boiler. Do not operate the unit with a known venting or gas issue.
- 1. Check venting: Go outside and inspect the Noritz boiler intake and exhaust terminals. Remove any leaves, snow, insect nests, or debris blocking airflow. Ensure vent screens are clear.
- 2. Verify combustion air: If the boiler is in a small or sealed room, make sure combustion air openings are not blocked by storage items or insulation. Restore required clearances per the installation manual.
- 3. Clean flame rod: With power and gas OFF, remove the front cover. Locate the flame rod near the burner. Gently clean it with fine emery cloth or a Scotch-Brite pad to remove oxidation. Do not bend the rod. Reinstall securely.
- 4. Inspect wiring: Check the flame rod and igniter wiring harness for loose connectors or damaged insulation. Reseat any loose plugs.
- 5. Test operation: Restore power and gas, then run the boiler. If error 12 persists, a technician should measure gas pressure and combustion values and may need to replace the flame rod or gas valve.
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Repair Difficulty
Hard
4/5
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