Furnace attempts to start but shows 6L error, multiple failed ignition attempts
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power and gas. Do not repeatedly reset a furnace that fails to ignite; unburned gas can accumulate.
Homeowner checks:
- Confirm gas supply: Ensure the main gas shutoff and appliance gas cock are fully open. Check if other gas appliances operate normally.
- Vent and intake: On sealed-combustion Buderus furnaces, verify that both intake and exhaust pipes are clear of ice, snow, or debris. Blocked venting can affect ignition.
- Filter and airflow: A severely clogged air filter can cause abnormal combustion. Replace the furnace filter if dirty.
Technician-level checks (do not attempt if untrained):
- Measure inlet and manifold gas pressure at the Buderus gas valve and compare to rating plate.
- Inspect and clean burner orifices and gas valve outlet.
- Test gas valve coil resistance and operation.
If 6L persists after basic checks, shut the unit down and schedule service with a Buderus-certified technician.
Repair Difficulty
Required Part
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