High Lockout
EE6 on Worcester Bosch WR325 RSF

Your boiler has detected an issue with the external valve system, preventing it from operating correctly and resulting in a total loss of heating and hot water.

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

External valve

What causes this fault?

This fault occurs when the boiler is unable to communicate with or operate the external valves that direct water to your radiators or hot water cylinder. The most common cause is a mechanical failure in the motorised valve head or a loose connection within the wiring center that manages your heating controls.

This fault is more frequent in autumn when heating systems are switched back on after a long summer break, often causing internal valve 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

EAView →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →