High Lockout
F3 on Ideal Logic Max Plus

Your boiler has detected an issue with the fan that safely clears exhaust gases, preventing it from starting up for your safety.

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

Fan fault

What causes this fault?

This fault occurs when the boiler's control board sends a signal to the fan to start, but either the fan fails to spin or the board doesn't receive confirmation that it is moving. The most common reason is a mechanical failure of the fan motor, though it can also be caused by loose electrical connections or a fault within the main circuit board itself.

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

L2View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →