High Lockout
1F on Vaillant Turbomax Pro 28 2E

Your boiler has suffered a major electrical failure where the internal fuse blows instantly, meaning the main control board has likely short-circuited and stopped working.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Does fuse F1 blow immediately? Check/replace fan or replace electronic board

What causes this fault?

This fault occurs when a component inside the boiler fails and draws too much electricity, causing the internal fuse to blow instantly to protect the system. The most common reason is a short circuit within the main control board itself or a failed internal pump that has suffered an electrical surge.

Engineer required

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

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