High
1021 B on Worcester Bosch 35 RSF

Your boiler's hot water sensor is not working correctly or has become unplugged, meaning the system cannot safely monitor the temperature of your tap water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

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