34
Noritz
Combustion Air Temperature Sensor Fault
Boiler displays error 34 and will not fire.
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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, Sensor wiring damage, Sensor exposed to abnormal heat from flue gas recirculation
How to Fix / Troubleshooting
Safety: Turn OFF power before servicing. Ensure venting is intact to avoid flue gas exposure.
- 1. Inspect venting: Check that the intake and exhaust pipes are correctly installed and not recirculating flue gases into the intake. Look for disconnected joints or melted sections.
- 2. Locate air sensor: Find the combustion air temperature sensor near the air intake path inside the Noritz boiler.
- 3. Check wiring and mounting: Ensure the sensor is firmly mounted and wiring is intact. Reseat the connector at the control board.
- 4. Replace sensor if needed: If error 34 remains, the sensor is likely defective and should be replaced by a technician, who should also verify proper venting and combustion.
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Repair Difficulty
Hard
4/5
Required Part
Combustion Air Thermistor
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