- Wed Sep 22, 2021 2:13 pm
#53211
If you take a close look at your sensor, there should be a Bosch number engraved on it. This is very helpful to identify the sensor. If it is Hall, it needs ground, +5 Volt to do a signal, which should change with a tooth or gap in front of it.
A VR sensor may have 3 pins too ( ground or signal -/ signal + / screen).
As you did not tell us the secret which Astra F you have got (maybe a 1.7 Diesel?) , no one can use the internet to find out for you, for example in your engines manual, which sensor you have got. Anyway, crank should be inductive = VR sensor with most Opelz. That does mean you need a VR conditioner of some kind on some Speeduino boards.
Leaving the input open, which is a very clever idea, simply not to connect things too complicated for you, leaves the input in an undefined stage, "floating". It may pick up any electrical noise from around the engine and show random readings if your installation is chaotic enough...
Good luck!