High Lockout
F.13 on Vaillant Turbomax 824/828

Your boiler has detected an electrical short circuit in its internal temperature sensor, causing the system to shut down for safety.

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

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What causes this fault?

This fault occurs when the boiler's internal temperature sensor develops an electrical short, preventing the system from accurately monitoring heat levels. The most common reason is that the sensor itself has failed internally, but it can also be caused by moisture getting into the wiring or a loose connection to the main control board.

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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