Bosch Poor Combustion / Sooting

Furnace ignites but produces yellow, lazy flames or soot at the flue terminal

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

Insufficient combustion air, Blocked burner or heat exchanger, Incorrect gas type or pressure, Flue recirculation of exhaust gases

Safety: Turn off the furnace immediately. Sooting indicates dangerous combustion conditions.

Air intake and flue: Check for obstructions and ensure the intake and exhaust are correctly installed and separated.
Burner cleaning: Clean burner and accessible heat exchanger surfaces of loose soot with a vacuum (wear a dust mask).

Combustion analysis and gas adjustments must be performed by a licensed technician with a calibrated analyzer.

Professional Required 5/5

Burner Assembly

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