Low
425 on Viessmann Vitodens 100-W B1KF-35

The boiler's internal clock couldn't update itself from its time signal, which is usually a minor issue that doesn't stop your heating or hot water working.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Time synchronisation failed.

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 100 W B1hf B1kf 6167586 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check the date and time shown on the boiler's controller and set them manually if they are wrong.Switch the boiler off at its power isolator or fused spur, wait about 30 seconds, then switch it back on.See whether the code clears. If it returns, or the clock keeps losing the correct time, contact a Gas Safe registered engineer to check the clock receiver or control unit.

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Related fault codes

424View →426View →

All 151 fault codes on the Vitodens 100-W B1KF-35

Seeing a different code? Every code this model can display, in one place.

78111213141516293049505758596263646567686970717273747577788789919295100102103104142161162163176182183184185299345346347348349350351352353354355357359361364365366367368369370371372373374375376377378379380381382383384385386387388395396399400401402403404405406408410416417418446447448449451452453454455456457458461462463464467468471474477517527528540544545574575576577578579682683684694738766767799979980981982E10E12

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