High
d3 on Worcester Bosch ZB 7 27 HE

Your boiler has detected a break in its internal safety circuit, meaning it has switched itself off to prevent potential overheating or operational risks.

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

Link missing or external limiter has pulled in.

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

d1View →E9View →

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