Low
S.96 on Vaillant ecoTEC plus 637

Your boiler is currently running a routine internal self-check on its water temperature sensors and has temporarily paused your heating or hot water to complete this process.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Return-sensor check is running, demand (DHW or heating) is blocked

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 637 4104465 installation & service manual, page 43.
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

S.97View →S.98View →

All 77 fault codes on the ecoTEC plus 637

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

Communication faultd.71F.00F.01F.02F.03F.10F.11F.12F.13F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.35F.42F.49F.52F.53F.54F.56F.57F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.76F.77F.78F.83F.84F.85F.91F.92F.93S.04S.10S.11S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.41S.42S.53S.54S.97S.98

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