High
F.012 on Vaillant ecoTEC Plus 836

Your boiler is struggling to accurately measure the temperature of the water it is heating for your taps, meaning you likely have no hot water available.

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.

What the manual says

Manufacturer manual

Fault in the electrical connection for the domestic hot water connection temperature sensor. Domestic hot water temperature sensor defective.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 80.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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.011View →F.013View →

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