High Lockout
F.70 on Vaillant ecoTEC Pro 28

Your boiler's main control board has lost its identity or is communicating incorrectly with the display unit, often following a part replacement.

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

Fault: Invalid Device Specific Number - Incorrect/missing Device Specific Number or incorrect/missing coding resistor

What causes this fault?

This fault occurs when the boiler's internal computer chips fail to recognize each other, essentially causing an identity crisis within the system. It most commonly happens after a new control board or display has been installed but hasn't been properly programmed with the specific code that matches your exact boiler model.

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.61View →F.62View →F.63View →F.64View →

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