High Lockout
LA on Ideal Classic FF

Your boiler has become too hot and has shut itself down as a safety precaution to prevent 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

OVER HEAT

What causes this fault?

This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety sensor to cut the power. The most common reasons are a failed internal pump that isn't moving the water away fast enough, or a build-up of sludge and debris blocking the flow of water through the system.

This fault often occurs during the first few cold days of autumn when the heating is turned back on after a long summer break, which can cause internal pump components to seize.

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.

Find a Gas Safe engineer
Search the official register →

Related fault codes

LFView →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →