Boiler runs but emits a strong smell of gas or combustion products
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
Critical safety warning: If you smell gas or suspect flue gas leakage, turn off the boiler immediately, ventilate the area, evacuate if necessary, and contact emergency gas services. Do not use naked flames or operate electrical switches.
- Shut down: Turn off the boiler and isolate gas at the service valve.
- Do not attempt repair: Flue and combustion issues must be handled by a qualified Viessmann service technician.
- Professional checks: A technician will perform a flue integrity test, combustion analysis, and inspect burner seals and heat exchanger for cracks.
Repair Difficulty
Required Part
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