Low Information
S.01 on Glow-worm Flexicom hx

Your boiler is currently preparing its internal fan to safely clear any leftover gases before it begins the ignition process.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

fan pre-run

What causes this fault?

This is not actually a fault, but rather a normal part of the boiler's starting routine where the fan spins up to clear the combustion chamber. It occurs every time there is a demand for heating or hot water to ensure the system is safe to ignite. If the code stays on the screen for a long time without the boiler firing up, it may indicate that the fan is struggling to reach the required speed.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

Find a Gas Safe engineer
Search the official register →

Related fault codes

S.00View →S.02View →S.03View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →