Medium Lockout
F18 on Vaillant ecoMAX Pro 28E

Your boiler's control panel has lost communication with the internal system, preventing you from adjusting settings or seeing the boiler's status.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Local user interface fault

What causes this fault?

This fault occurs when the communication link between the display panel you interact with and the boiler's main internal brain is broken. The most common reason is a loose or damaged connection on the internal wiring, though it can also be caused by an electronic component on one of the control boards failing due to age.

DIY fix possible

Locate the main power switch for the boiler (fused spur).Turn the power off for 60 seconds.Turn the power back on to see if the control panel restarts and clears the error.

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