CH light On (flashing) Medium

Worcester Bosch CH light On (flashing) Fault Code

Also written as CHLIGHTONFLASHING — same fault.

The Worcester Bosch CH light On (flashing) fault code means: your boiler has temporarily stopped itself because it detected that the water inside is getting too hot, but it will attempt to restart automatically after a short cooling period.. 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: Over temperature shut-down if flow temperature 5°C above set value. Three minute wait.
Typical repair cost £120-250 (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 CH light On (flashing) fault code

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

Source

Worcester Bosch CH light On (flashing) 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 7 July 2026