High
235 on Worcester Bosch Junior 28i

Your boiler’s internal computer and main control parts are unable to talk to each other because their software versions do not match.

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

Incompatible heat control module (HCM) software versions – control box needs latest software

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

E9View →A1View →

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