High
F.1 on Vaillant Ecomax Condensing 600/800 series

Your boiler is struggling to accurately measure the temperature of the water returning to it, which prevents it from heating your home safely and has caused it to shut down for protection.

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

Return–NTC: – NTC broken – NTC cable broken – Defective connection at NTC – Defective connection at electronics | Return–NTC cable defective/broken NTC faulty

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.0View →

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