High Lockout
9.E on Worcester Bosch Greenstar CDi Compact

Your boiler is struggling to detect when you turn on a hot tap, meaning you might have inconsistent or no 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

Turbine signal delay (combi only)

What causes this fault?

This fault occurs when the boiler's internal sensor fails to detect water moving through the system quickly enough after you open a tap. It is usually caused by a sticking flow turbine that can't spin freely or a failing diverter valve that is struggling to switch the water flow from heating to hot water mode.

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 →D1View →

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 →