High Lockout
Fast flash on Worcester Bosch Greenstar 12Ri

Your boiler has detected a critical internal fault and has locked itself out to prevent damage or unsafe operation.

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

Volatile lockout (sensor, fan or code plug): Temperature sensor (8000 - 20000Ω); Wiring/connections to sensor; Fan/cable/connections; Code plug fitted.

What causes this fault?

This fault occurs when the boiler's internal computer detects a conflict or failure in its safety sensors or the fan that clears exhaust gases. The most common reason is that a sensor has stopped reporting the correct temperature or the fan is no longer spinning at the required speed, causing the system to shut down for safety. Since the boiler cannot confirm the system is venting or cooling correctly, it locks itself out to prevent overheating.

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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