BoilerFaultCodes.com
LED 3 lit High Lockout

Your boiler is trying to start its cycle but has detected an electrical issue that is preventing the internal fan from running safely.

Call an engineer soon

Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Condition for fan operation on the PCB.

What causes this fault?

This fault occurs when the boiler's control board sends a signal for the fan to start, but it fails to detect the correct electrical response to confirm it is spinning safely. The most common reason is an internal electronic failure on the main circuit board or a mechanical breakdown within the fan motor itself. Without the fan running to clear exhaust gases, the boiler will stay in a safe shutdown mode.

This fault is slightly more common in winter when the fan has to work harder and run for longer periods to meet higher heating demands.

Typical repair cost £180-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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