Sensor error
Vaillant vSMART Internal Temperature Sensor Fault

vSMART thermostat or app displays a generic 'Sensor error' and cannot regulate temperature correctly.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failed NTC temperature sensor in vSMART room unit, damaged sensor wiring on PCB, exposure to moisture or condensation inside thermostat housing, firmware misreading sensor values

How to Fix / Troubleshooting

Safety: Do not open the thermostat if it is under warranty; this may void coverage. Work only on low‑voltage parts.

Steps to address sensor error:

  • Reboot the thermostat: Remove power (or batteries) for 1–2 minutes, then restore power and check if the error clears.
  • Check location: Ensure the thermostat is not installed above a radiator, in direct sunlight, or near a draught, as extreme conditions can trigger sensor protection or misreadings.
  • Inspect for moisture: Look for signs of condensation or water ingress on or around the thermostat. If present, dry the area, improve ventilation, and avoid using the device until fully dry.
  • Update firmware: Use the Vaillant app to check for and apply any firmware updates that may correct sensor calibration or reading issues.

If the error persists and the thermostat shows obviously incorrect temperatures, the internal NTC sensor or PCB is likely defective. Replacement of the vSMART room unit by a qualified technician is recommended.

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Repair Difficulty

Medium 3/5

Required Part

vSMART Room Thermostat (Internal NTC Sensor)
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