Hutkikz:
Good read for anyone wanting to put electronics in their car.suppression_of_transients_in_an_automotive_environment_application_note.pdf
Thank you for this, an interesting read.
If you put in a voltage divider this will reduce the volts.
If you add a zenar diode (5v) on the input pin inconjunction with a inline resistor this will stop voltage spikes.
Another diode inline will stop the reverse voltage.
And there you have a basic system.
Thanks to all