BoilerFaultCodes.com
1 2. High Lockout

Your boiler's internal electronic protection has triggered and the unit has completely lost power due to a failed internal fuse.

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: Control fault: Fuse F1 (3.15 AT) defective.

What causes this fault?

This fault occurs when the boiler's internal safety fuse blows to protect the sensitive electronics from an electrical surge or component failure. The most common reason is an internal leak or a failing water pump that has short-circuited and drawn too much power. Because the fuse has blown, the boiler acts as if it has no power at all and will stay completely dark until the fuse and the faulty part are replaced.

This fault is more common at the start of winter when the heating is first turned on, as pumps that have been sitting idle over summer are more likely to seize and cause an electrical short.

Typical repair cost £90-180 (including labour)

Engineer required

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

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