ok well heres the problem.i just bought an 89 fastback,the previous owner had replaced the factory head unit with an aftermarket one.He did this without a wiring harness and just spliced everything in.i took out the old unit and began to splice in my own deck.when i had finished, everything worked great until i put my headlights on.when i put on my headlights the deck(its a blaupunkt cd52 heidelberg)turns off. i tried this a few times and no go until the headlight and interior lights went out.it ended up blowing a fuse.i replaced the fuse but the cd deck is still turning off whenever i switch the headlights in the on position.do any of the interior or exterior lights or switch wires run to the audio unit?any ideas what this could be?

 

ok figured it out.im a retard.i had the ground wire of my head unit connected to another wire which i thought was a ground wire.i attached the ground wire to the audio plate and it works fine now.kinda scary that the previous owner somehow had this setup working it looks like the ground wire was hooked up to maybe a dimmer wire or something of that sort,i have no idea why this worked for him.but anyway mine works so im happy