High
F78 on British Gas 330+

Your boiler has lost communication with its external controls or internal wiring kit, preventing it from heating your home.

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.

What the manual says

Manufacturer manual

Wrong configuration of accessory. Intelligent Wiring Kit connected but connector on main PCB (X2) not connected. Check connection.

From this model's manual
Verified against the British Gas 330 installation & service manual, page 45.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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

F77View →F27View →

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