High
F4 on Heatline Capriz 25/28

Your boiler has effectively switched itself off because it has detected it was getting too hot, usually caused by a blockage or a pump failure.

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

Thermal fuse / Limit thermostat fault

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

F1View →F3View →F5View →

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