Medium
F.03 on Vaillant ecoTEC plus 937

Your boiler has detected a faulty connection or sensor inside the built-in hot water storage tank, which means your hot water supply may be affected.

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

Shift load storage tank temperature (NTC) open circuit, only in combination with F.91 - NTC faulty, NTC cable faulty, faulty plug connection on NTC, faulty plug connection on the electronics

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 937 Vui Gb 376 3 5 Isim installation & service manual.
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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Related fault codes

F.91View →F.02View →

All 38 fault codes on the ecoTEC plus 937

Seeing a different code? Every code this model can display, in one place.

conF.0F.01F.02F.10F.11F.12F.13F.20F.22F.23F.24F.25F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.70F.71F.72F.73F.74F.75F.76F.77F.78F.80F.81F.90F.91

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