H13 on a Worcester Bosch boiler means: annual service reminder. This is a reminder rather than a fault — the boiler keeps working.
This is a maintenance message, not a fault — the boiler keeps working.
This code applies to Worcester Bosch Greenstar Si Compact, Greenstar i and CDi Compact. Codes can mean different things on different models, so check the display against your boiler's user manual.
What you can safely check
- Book your annual service with a Gas Safe registered engineer. Many manufacturers need yearly servicing to keep the warranty valid.
- Your user manual explains how the reminder is cleared — usually by the engineer at the service.
When to call an engineer
Any Gas Safe engineer can carry out the service and reset the reminder.
Never remove the boiler casing yourself — everything behind it must be handled by a Gas Safe registered engineer. If you smell gas, open windows, turn the gas off at the meter, and call the National Gas Emergency number on 0800 111 999.
Repair it, or replace it?
If your boiler is over 10 years old, compare a repair against a new combi before you pay for parts.
Applies to: Worcester Bosch Greenstar Si Compact, Greenstar i and CDi Compact
Meaning checked against: HomeServe — Worcester Bosch boiler faults
Last reviewed November 2026. Always follow your boiler's own user manual.