High Lockout
E4 on Worcester Bosch WR325 RSF

Your boiler has detected a problem with how it controls the gas flow, meaning it cannot safely regulate the flame and has shut down as a precaution.

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

Fault with the gas modulator

What causes this fault?

This fault occurs when the boiler's main control board loses the ability to vary the amount of gas entering the burner, which is necessary to maintain the correct water temperature. The most common reason is an electrical failure in the solenoid coil that moves the gas valve, or a communication error from the circuit board itself. Because the system can no longer precisely control the size of the flame, it shuts down to ensure your home remains safe.

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

EAView →E9View →

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