Emergency
F on Worcester Bosch 24i / 28i Junior

Your boiler has detected an internal control setting issue with the gas valve switch, which prevents it from operating safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Flash 4 times per second: Gas Valvemode switch on min or max.

Shared across the 24i / 28i Junior range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
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 emergency 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

EAView →D1View →

All 27 fault codes on the 24i / 28i Junior

Seeing a different code? Every code this model can display, in one place.

24i28i200203208265AA1A8BCDEF1F2Flash once per secondGHILight onNo CH function (DHW OK)No DHW function (CH OK)No lights and no functions (with demand)rET1T3

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