BoilerFaultCodes.com
A08 High Lockout

Your boiler has detected an internal electrical safety failure and has shut down to prevent damage or unsafe operation.

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: Safety relay open when should be closed

What causes this fault?

This fault occurs when the boiler's internal computer detects that a critical safety switch on the circuit board has failed to move into the correct position. The system shuts down immediately because it can no longer verify that the gas and ignition components are being controlled safely. The most common reason is that the electrical contacts on the main control board have worn out or become stuck over time.

Typical repair cost £180-450 (including labour)

Engineer required

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

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Protect yourself from future repair bills

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