High Lockout
F70 on Vaillant ecoTEC Plus 625

Your boiler's computer brains are not talking to each other correctly because a security code needs to be re-entered after a repair.

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

After replacing both components, after being turned on, the appliance goes to fault and displays the error message “F70”.

What causes this fault?

This fault occurs when the boiler's main control board and the display screen are not compatible or have not been properly introduced to each other. It usually happens after a repair where one of these parts was replaced but the unique software code for your specific boiler model wasn't entered. Without this identity code, the two components cannot communicate and the boiler will not fire up for safety reasons.

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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