High Lockout
LED 1 Fast Flashing (8Hz) on Glow-worm Micron 40FF

Your boiler’s internal control board has developed a critical electronic fault and can no longer manage the heating process safely.

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

PCB Failure

What causes this fault?

This fault occurs when the boiler's internal electronic brain suffers a hardware failure, preventing it from processing information from the sensors. The most common reason is the natural degradation of electrical components on the circuit board over time, or a sudden voltage spike that has damaged the delicate circuitry. Because the board can no longer guarantee the boiler is operating safely, it shuts the system down entirely.

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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