Medium
F.03 on Vaillant ecoTEC plus 938 VUI 286/5-5 R6

Your boiler has lost connection to the temperature sensor inside its built-in hot water storage tank, meaning it cannot properly monitor or heat your stored hot water.

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

Cylinder temperature sensor interruption

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 938 Vui 286 5 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.04View →F.05View →F.06View →

All 59 fault codes on the ecoTEC plus 938 VUI 286/5-5 R6

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

F.00F.01F.02F.10F.11F.12F.13F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.42F.49F.52F.53F.54F.55F.56F.57F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.78F.80F.81F.82F.83F.84F.85F.90F.91F.92F.93F.94S.88S.92S.93S.96S.97S.98S.99

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