12
Noritz
Flame Loss / Flame Rod Detection Failure
Burner lights briefly then goes out; display shows error code 12; intermittent hot water that quickly turns cold.
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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
Dirty or corroded flame rod, Poor ground connection, Low gas pressure during operation, Faulty flame sensing circuit on PCB
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas before removing the front cover. Allow the unit to cool completely.
Steps to check and correct:
- Clean the flame rod: Locate the flame rod (flame sensor) near the burner assembly. Remove the mounting screw and gently pull out the rod. Clean the metal probe with fine steel wool or a Scotch-Brite pad to remove oxidation and soot. Do not scratch the ceramic insulator. Reinstall securely.
- Check ground connection: Verify that the ground wire from the PCB to the chassis is tight and free of corrosion. Tighten any loose screws and clean contact points if rusty.
- Inspect burner surface: Look for heavy rust, debris, or spider webs on the burner. Clean with compressed air or a soft brush. Do not deform the burner ports.
- Verify gas supply under load: If possible, have a technician measure gas pressure at the inlet while the unit is firing. Low dynamic pressure can cause flame dropout and error 12.
- Reset and test: Restore power and gas, then run hot water. If error 12 returns, the PCB flame sensing circuit or gas valve may be defective and should be diagnosed by a Noritz-authorized service provider.
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Repair Difficulty
Hard
4/5
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