High
3.3 on Worcester Bosch ZWB 7-25

Your boiler is struggling to detect the flame needed to heat your home and has shut down as a safety 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

Check ionisation current, Service Function 3.3. If the display shows 0 or 1, the electrode assembly must be cleaned or replaced.

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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