Make sure all your grounds are good and properly done. Try grounding the case of the carputer and PSU. Are you using an inverter or a DC\DC PSU? If using an inverter try using a single outlet noise\line filter.
I hooked my pc to the auxilary input of my Blaupunkt San Jose. The sound is good, I got it hooked to the right pins, but there is some alternator whine. The stereo sounded great before I hooked the pc up. Should I install a line level input filter on the output line of the pc? Would this remedy the situation?
2000 Grand Am GT PC