High Lockout
F61 on Glow-worm Ultracom 2 CXI

Your boiler has detected an internal communication failure between the main control board and the gas valve, meaning it cannot safely light the flame.

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

Main PCB gas valve control fault

What causes this fault?

This fault occurs when the boiler's main computer loses the ability to send or receive signals from the gas valve, which is the component that controls the flow of fuel. The most common reason is an electronic failure within the circuit board itself or a loose connection in the internal wiring. Because the boiler cannot confirm it can safely control the gas supply, it shuts down as a safety precaution.

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

F62View →F22View →F28View →

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 →