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.
Solutions
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
0020068120 Buy on Amazon
193592 Buy on Amazon Buy on eBay
A Gas Safe professional must confirm the part number against the boiler GC number before ordering or fitting. Use 193592 or 0020068120 only when that number matches the boiler — they are not interchangeable on every appliance.
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