Low
4-b1 on Worcester Bosch Greenstar 2000

Your boiler is simply indicating whether its internal weather-monitoring feature is currently turned on or off.

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

Device-internal weather-compensated control: OFF: not active, ON: active.

DIY fix possible

Locate the boiler's control panelNavigate to the secondary settings menuEnable or disable the 'Weather Compensation' setting based on your preference

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

New boiler cost 2026

Realistic UK prices for a swap.

Read →