Code 34
Rinnai Combustion Air / Flue Thermistor Fault

Unit displays Code 34; may occur during windy conditions or vent issues

Advertisements

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.

Advertisements

Possible Causes

Faulty combustion air thermistor, Loose or damaged wiring, Overheating at flue due to vent blockage, Faulty control board

How to Fix / Troubleshooting

Safety first: Turn OFF gas and power. Vent and flue components can be hot; allow cooling before inspection.

Steps to check:

  • Inspect vent system: Ensure intake and exhaust are clear and vent piping is intact and properly supported.
  • Locate combustion air/flue thermistor: Typically mounted near the exhaust outlet or in the flue collar.
  • Check wiring: Verify the thermistor harness is secure and undamaged.
  • Reset and test: After inspection, restore power and gas and reset the unit.

When to call a professional: If Code 34 persists, a technician should test the thermistor and evaluate vent design and combustion.

Advertisements

Repair Difficulty

Hard 4/5

Required Part

Flue Gas Thermistor
Check Price on Amazon

We may earn a commission from links on this page.

Advertisements