High Lockout
15 on Glow-worm Xtramax HE

Your boiler's gas control mechanism has stopped moving correctly, which means the system cannot safely regulate the fuel it needs to stay alight.

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

STEP MOTOR FAILURE: MOTOR CONNECTION OR MOTOR FAILURE.

What causes this fault?

This fault occurs when the small internal motor that regulates the gas supply fails to move into the correct position. The most common reason is that the motor's internal components have worn out or become physically stuck, meaning the boiler can no longer safely control the amount of fuel entering the burner.

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

F7View →F13View →F16View →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →