Soot or dark staining appears around the flue terminal or furnace casing.
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 gas and power immediately. Sooting indicates dangerous combustion conditions.
Do not operate the furnace until it has been inspected.
Professional tasks only: A licensed technician must clean the burner and heat exchanger, check the flue for blockage, verify combustion with an analyzer, and adjust gas settings according to Cointra specifications.
Repair Difficulty
Required Part
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