High Lockout
con on Vaillant ecoTEC exclusive

Your boiler's internal computer brain is unable to talk to the front display panel, meaning the system cannot receive instructions to provide heating or hot water.

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

No communication with the printed circuit board: Communication fault between the display and the printed circuit board in the switchgear box

What causes this fault?

This fault occurs when the 'handshake' between the boiler's main control board and the front display panel is interrupted. The most common reason is a loose or damaged connection cable internally, though it often signifies that the electronics have suffered a surge or a component failure on one of the boards.

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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Related fault codes

F.49View →F.70View →

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