BoilerFaultCodesViessmann 35 Fault Code
The Viessmann 35 fault code means: your boiler has failed to ignite or stay lit, meaning your heating and hot water have stopped working.. It appears on 12 Viessmann models in our database.
Technical description: Boiler does not activate
What causes the Viessmann 35 fault?
This fault occurs when the boiler's control system cannot confirm that a flame has been successfully established after several attempts. The most common reasons are a worn-out component that senses the flame, a lack of gas reaching the burner, or a build-up of carbon deposits on the ignition parts.
This issue is more frequent during the first cold snap of autumn, as ignition components that have sat idle or were already weakened can fail when suddenly asked to work under higher demand.
DIY fix possible
Check if your gas supply is active by testing another gas appliance like a hob.Try resetting the boiler using the 'R' or reset button on the control panel.Ensure your system pressure is between 1.0 and 1.5 bar on the pressure gauge.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Viessmann models that show the 35 fault code
Click a model for the full fault code list and model-specific repair notes.
- A8 Repair: £150-350
- Vitodens 050-W Repair: £120-450
- Vitodens 100-W / 200-W Repair: £120-450
- Vitodens 111-W Repair: £120-450
- Vitodens 200 Repair: £120-450
- Vitodens 200-W Repair: £120-450
- Vitodens 222-W Repair: £120-450
- Vitodens 333-F Repair: £120-450
- Vitola Biferral Repair: £180-450
- Vitopend 100 Repair: £120-300
- Vitopend 111 Repair: £120-350
- Vitorond 100 Repair: £120-280
Source
Viessmann 35 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026