High
F.01 on Vaillant ecoTEC Plus 826

Your boiler has lost its connection to a sensor that measures the water returning to the system, causing it to stop heating as a safety precaution.

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

Returntemperaturesensor interruption

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

F.00View →

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