Fault 51 127 Medium

Worcester Bosch Fault 51 127 Fault Code

Also written as FAULT51127 — same fault.

The Worcester Bosch Fault 51 127 fault code means: your boiler's control system has detected that the wrong type of temperature sensor has been installed or configured for your hot water system.. It appears on 1 Worcester Bosch model in our database.

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: Cylinder temperature sensor type used as collector temperature sensor (TA).

What causes the Worcester Bosch Fault 51 127 fault?

This fault occurs when the boiler's internal computer detects a mismatch between the temperature sensor installed and the settings it is expecting to see. It most commonly happens if the wrong part was used during a recent repair or if the control board has developed a software glitch that misidentifies the hot water components.

Typical repair cost £90-180 (including labour)

Engineer required

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

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Worcester Bosch models that show the Fault 51 127 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch Fault 51 127 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026