Justscary:
Thankyou, I shall, would you know if I would have to do it to the earth only or to all the inputs, the other inputs read the alternator so am I able to presume they are electrically isolated from the earth noise?
Sorry I think your English fell apart there so I am not sure what you said.
You need everything to share a common ground, read:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
and
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html