BoilerFaultCodesVaillant L.105 Fault Code
Also written as L105 — same fault.
The Vaillant L.105 fault code means: your boiler has failed to remove air from its internal system during the start-up process, meaning it cannot begin heating your water safely.. It appears on 3 Vaillant models in our database.
Technical description: The unit is not purged correctly. The purge programme could not be completed successfully.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like L.105: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Vaillant models that show the L.105 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant L.105 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026