Code 29 = Combustion fan fault. Control board commanded the fan to start (or run at a specific RPM) and either didn't receive expected RPM feedback or fan didn't respond.
Diagnostic sequence
1. Listen for the fan
When the unit attempts to fire, you should hear the fan ramp up. If silent — fan motor dead, power lead disconnected, or PCB output failure.
2. Inspect air inlet
Fan heavily loaded (intake blocked) may not reach commanded RPM, triggering Code 29. Clean the intake filter and inspect vent termination.
3. Wiring
Power harness from PCB to fan motor — loose connector or damaged pin. Visual + multimeter check.
4. RPM feedback wire
Noritz fan assemblies include a Hall-effect RPM sensor. If sensor or return wire fails, fan spins but PCB throws Code 29 because it can't confirm RPM.
5. Fan motor
If motor is bad, replacement is dealer-level. Fan assembly (fan + motor + housing) is typically one SKU. $150-300 parts.
Reset procedure
- Power cycle the unit
- Listen carefully for the fan during ignition
- If silent, escalate to wiring/motor diagnosis
- If audible but Code 29 returns, RPM sensor or feedback wire
Common scenarios
- Code 29 only in winter: intake icing
- Code 29 + grinding/noisy fan: bearings failing, replace fan assembly
- Intermittent Code 29: loose harness connector
Bottom line
Code 29 is hardware — fan or RPM sensor. Cleaning intake and re-seating connectors resolves a meaningful fraction. Persistent Code 29 = installer call.