High Lockout
E03 on Ravenheat CSI 120

Your boiler has detected an issue with the sensor that monitors water movement, preventing the system from heating up properly.

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

Flow sensor damaged

What causes this fault?

This fault occurs when the boiler's control board loses communication with the sensor that tracks water moving through the system. The most common reason is that the internal components of the sensor have worn out or developed a spiritual fault, meaning the boiler cannot confirm it is safe to fire up without risking overheating.

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

E02View →E05View →

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