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Vaillant · Heat pumps · Vaillant aroTHERM plus with uniTOWER plus

F.703Sensor fault: Low pressure

Name in the manufacturer's documentation (service manual): Sensor fault: Low pressure[1]

In plain words (editorial)

Fault of the low-pressure sensor in the refrigerant circuit. The manual names the cause: the sensor is not connected or its input has short-circuited. The fix (checking or replacing the sensor or its wiring harness) is a job for a competent heating engineer.

When to call a service technician: Contact a competent heating engineer (installer or Vaillant customer service).

✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.

The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →

Sources

Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.

  1. [1] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 60 official manufacturer document quote verified F.703 Sensor fault: Low pressure
  2. [2] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 60 official manufacturer document quote verified The sensor is not connected or the sensor input has short-circuited
  3. [3] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 60 official manufacturer document quote verified Checking the sensor (e.g. using an installation aid), and replacing it if necessary
  4. [4] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 60 official manufacturer document quote verified Replace the wiring harness