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Andrew GomezJul 26, 2025
Why does my Viessmann Boiler burner not switch on or only work sometimes?
- MMax SullivanJul 26, 2025
The burner might not be switching on, or may only intermittently switch on, due to several reasons. First, check if the gas shut-off valve is open, as there might be no gas. Also, the control unit may be incorrectly programmed or set, so check and correct the settings of the heating program selector switch and timer programming if necessary. Finally, there may be a fault on the control unit, in which case you should inform your heating contractor. As a temporary measure, after consulting with your heating contractor, you can operate the boiler at a constant water temperature using the override/emissions test switch 'S'.
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