Medium
F.13 on Vaillant Ecomax Condensing 600/800 series

Your boiler is struggling to accurately read the temperature of your hot water cylinder because there is a faulty electrical connection or sensor.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Short circuit in tank sensor. Cause: NTC defective, earth leak/short circuit in cable loom, damp plug connection

From this model's manual
Verified against the Vaillant Ecomax Condensing 600 800 Series installation & service manual, page 49.
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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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