High Lockout
S.97 on Glow-worm Flexicom hx

Your boiler is temporarily pausing to check if there is enough water pressure before it starts up, which is preventing your heating and hot water from running.

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

Water pressure sensor check is running, demand (DHW or heating) is blocked

What causes this fault?

This fault occurs when the boiler's internal computer tries to verify there is enough water pressure to run safely but fails to get a clear reading. The most common reason is a failing or blocked water pressure sensor that provides inconsistent data, causing the system to pause 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

F22View →F24View →S.07View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →