Low
H03 on Worcester Bosch Greenstar Heatslave II

Your boiler is struggling to read the temperature outside, which may cause it to run less efficiently than usual.

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.

What the manual says

Manufacturer manual

Outdoor sensor not fitted/detected or outdoor sensor is open circuit or closed circuit

From this model's manual
Verified against the Worcester Bosch Greenstar Heatslave Ii installation & service manual, page 43.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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