Low Warning
CC800 on Worcester Bosch CDi Classic

Your boiler has lost communication with its outdoor temperature sensor, meaning it won't be able to adjust its energy use based on the weather outside.

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

What causes this fault?

This fault occurs when the main control board can no longer detect a signal from the weather compensation probe located on the outside of your home. The most common reasons are moisture getting into the sensor housing or the thin communication wires becoming damaged or disconnected due to wind and garden work.

This fault is often noticed during autumn or early winter when the boiler first attempts to use more advanced heating curves to respond to dropping outdoor temperatures.

Engineer required

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

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Related fault codes

A7View →A8View →

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