High Lockout
Overheat 'stat trip on Ideal Classic FF

Your boiler has become too hot and has automatically switched itself off to prevent any damage.

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

Boiler exceeds 90°C or faulty thermostat. Reset by pressing the reset button (D)

What causes this fault?

This fault occurs when the water inside the boiler reaches a dangerously high temperature, causing a safety switch to cut the power. The most common reasons are a pump failure that stops water from moving around the system or a build-up of sludge that blocks the heat exchanger. In some cases, the thermostat itself may have simply worn out and is giving a false reading.

This fault often appears during the first cold snap of autumn when a pump that has been sitting idle all summer becomes seized or stuck.

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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