High
E04 on Atag A200

Your boiler has detected an issue with the sensor that monitors water returning from your radiators, which may stop the system from heating effectively.

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

°C return water temperature T2

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

E01View →E02View →E05View →

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