Low
CC 800 on Worcester Bosch Heatslave

Your boiler has lost communication with the sensor that monitors the temperature outside, which may cause your heating to run less efficiently.

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

Outdoor sensor defect available when accessory outdoor sensor is connected

DIY fix possible

Check the outdoor sensor for any obvious physical damage or loose wiresClear any debris, ice, or vegetation that may be covering the sensorRestart the boiler to see if the error clears

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

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 →