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F.85

F.85 - Flow and return temperature sensors incorrectly installed

Vaillant · ecoTEC plus Boilers

What does F.85 mean?

The flow and return temperature sensors have been physically installed on the same pipe or on incorrect pipes, leading to incorrect temperature readings.

Common Causes

  • The flow and/or return temperature sensors have been installed on the same pipe or an incorrect pipe.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Press the reset button on the boiler display up to three times to try and clear the fault.

  2. 2

    Contact customer service. This fault specifically indicates that the flow and return temperature sensors are physically installed incorrectly on the pipework.

  3. 3

    A qualified technician will be required to re-install the sensors in their correct positions.

Browse all codes in this manual (146)
Verified technical data. Last updated: April 2026

Related Faults

Communication fault (display/PCB)Communication fault - No communication with the PCBD.092 = 1D.092 = 1 — actoSTOR module connection errorF.0F.0 — Flow–NTC open circuit
Source: Vaillant ecoTEC plus Boilers
Open Manual (Page 48)Search more codes in this manual