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Vaillant F72 Fault Code

Welcome to the fault-codes section of this site. The following table or page contains the information required to help repair and diagnose the fault codes being shown on the boiler display. You may be guided through the fault finding sequence or steps, for rectifying your boiler with this fault code. Suggested repair solutions may be provided by a link to a repair page. NB Some fault codes are only applicable to a specific range of boilers only.

F.72 Meaning

This fault according to Vaillant Instructions and Servicing manual is a Flow and/or return NTC fault, whereby the temperature difference between the Flow and Return NTC sensors are too high.

Cause of F72

Specifically Flow and/or Return NTC is defective, caused by tolerances too big. In simple terms, the reading being reported are not in line with manufacturers expected readings.

Models applicable to:

Ecotec Pro, Ecotec Plus, Ecotec Exclusive.


Before simply replacing the NTC sensors or jumping to conclusions.

  • Things to check:
  • Make sure the resistance of the Flow NTC is 12K ohms at 20C (degrees celcius).
  • Make sure the resistance of the Return NTC is also 12K ohms at 20C (degrees celcius).
  • You should check the connections from the NTC all the way back to the PCB. Removing and re-inserting carefully. Using a multimeter, you can test the wiring harness to make sure there is no break or partial break in the cable.
  • Check the X20 Connector of which the NTC harness is connected to.
  • That the NTC sensors are on the correct pipe. Usually blue wire is the Heating Return NTC and the red wire is the Heating Flow NTC


Part Numbers

NTC Flow / Return Sensor



Vaillant NTC Sensor 0020068120
Vaillant NTC Sensor 0020068120
Vaillant Flow / Return NTC 193592
Vaillant Flow / Return NTC 193592

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