Emergency
F.68 on Viessmann Vitodens 100-W WB1A

Your boiler is detecting a flame inside before it has actually tried to turn on, which means the safety system has locked out the unit to prevent it from starting incorrectly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Flame signal is already present at burner start.

From this model's manual
Verified against the Viessmann Vitodens 100 W Wb1a installation & service manual, page 85.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.67View →F.69View →

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