Emergency
363 on Worcester Bosch 1000

Your boiler has detected that the flame is remaining active when it should have shut off, preventing it from starting 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.

Technical description

Ionisation current did not drop during ionisation test

What causes this fault?

Ionization test failure

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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