Medium Lockout
51122 on Worcester Bosch Greenstar CDi Compact

Your boiler is confused because the wrong type of temperature sensor has been plugged into the system, meaning it can't accurately monitor your hot water cylinder.

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

Incorrect temperature sensor type connected Collector temperature sensor type used as cylinder temperature sensor (T2).

What causes this fault?

This fault occurs when the boiler's control board detects a signal from a temperature sensor that doesn't match the expected specifications for your hot water cylinder. It most commonly happens because an incorrect or incompatible part was installed during a repair, or because an internal electrical fault has caused the sensor to send a confusing signal to the boiler.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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