34
Noritz
Combustion Air Temperature Sensor Fault
Error code 34 displayed; unit may shut down or fail to start.
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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
Failed combustion air thermistor, Wiring harness damage, Sensor connector loose at PCB, Sensor exposed to abnormal temperatures
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas before opening the unit.
Steps to check and correct:
- Locate combustion air sensor: On many Noritz models, this thermistor is located near the air intake or fan housing.
- Inspect wiring: Look for pinched or melted wires, especially near the fan and flue area. Repair or replace damaged wiring.
- Reseat connectors: Disconnect and reconnect the sensor plug at both ends to ensure good contact.
- Test sensor: Measure resistance and compare to Noritz specifications. Replace the combustion air thermistor if readings are incorrect.
- Reset and test: Restore power and run the unit. If error 34 continues, the PCB input circuit may be faulty and should be checked by a Noritz technician.
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Repair Difficulty
Hard
4/5
Required Part
Combustion Air Thermistor
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