The flame rod (flame sensor) is a small metal probe that detects flame presence by micro-current. Carbon and oxidation buildup degrades the signal — control board misreads as no-flame and shuts the unit down. The single most-replaced Noritz part, behind a large fraction of Code 11 and Code 12 faults on units 5+ years old.
Symptoms
- Intermittent Code 12 (flame failure mid-operation)
- Persistent Code 11 (no ignition) on older units
- Unit takes multiple attempts to light
- Burner cycles on/off during a single draw
Clean first (free)
- Power off and shut off gas
- Remove the front cover
- Locate the flame rod — small metal probe in burner area with one or two-wire connection
- Unscrew or unplug the rod
- Clean with fine sandpaper (400-grit) or Scotch-Brite. Polish until bright metal. Don't bend
- Reinstall, close, power on, test
Cleaning resolves about 60% of cases on units 5+ years old.
Replace if cleaning doesn't work
Noritz flame rods are model-specific — get the part number from the parts diagram. Cost: $25-70 OEM. Replacement procedure is identical to cleaning.
DIY vs dealer
Flame rod cleaning is fully DIY — 20 minutes, no tools beyond a screwdriver. Replacement is also DIY-safe.
Inside warranty
Covered under 5-year parts warranty. Contact Noritz support for warranty replacement shipped to your installer.
Why does it fail?
Normal carbon buildup from combustion. Propane systems build up faster. Hard water regions: exchanger scale changes burner flame characteristics, depositing more carbon. Annual maintenance extends rod life.
Bottom line
Before calling anyone about Code 11 or 12, clean the flame rod. Free, 20 minutes, the most common fix.