Emergency
363 on Worcester Bosch Greenstar 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.

What the manual says

Manufacturer manual

Ionisation current did not drop during ionisation test

From this model's manual
Verified against the Worcester Bosch Worcester Bosch Greenstar 1000 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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