L2
Buderus Flue Gas Overtemperature / Limit Exceeded

L2 code, furnace shuts down, may restart after cooling

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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

Blocked or undersized flue, Excessive soot in heat exchanger, Failed flue gas sensor, Incorrect burner adjustment causing high stack temperature

How to Fix / Troubleshooting

Safety: Turn off power and gas. Do not operate a furnace with suspected flue blockage; risk of carbon monoxide.

Steps:

  • Check vent termination: Inspect the outdoor exhaust for obstructions (ice, nests, debris). Clear any blockage.
  • Visual inspection: Look into the flue connection at the furnace for signs of heavy soot or collapsed liner. Do not dismantle venting beyond what is accessible without tools.
  • Flue sensor check: Ensure the flue gas sensor is firmly mounted and wiring is intact.

Because L2 indicates a potentially dangerous flue condition, a certified Buderus technician should inspect the entire vent system, clean the heat exchanger, and verify combustion with instruments.

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Repair Difficulty

Professional Required 5/5

Required Part

Buderus Flue Gas Temperature Sensor
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