I have a double dash connected to a harness. And I need to tap into these wires twice for an navigation module and an lcd.
I would have to say once. And thats even cutting it close. You should never tap into any stock wires. They are mainly for running your car with nothing else.
it is likely the old units chassis slides into a metal frame, that is a chassis ground, that or like gordy sayz thru the antenna, he all so went on to say you need to find anything metal to ground, look for a screw or drill a hole, make sure the paint is scraped off, the new unit may have a connection to put a screw thru if not u have to attach one, make sure the screw is turned down tight to have as much contact to the cars metal as possible. avoid extending the ground wire, buy a multimeter for less then 20.oo to test wires it is a good investment for a diyer.
your not going to want to tap into those wires get it hooked up right or you run the risk of overloading the factory wiring resulting in popping fuses or much worse complete electric malfunction, another easy way is to get a wiring kit with inline fuses and a switch and hard wire it with a switch , but i would go to a shop if i were you , should only be 45 to 75 bucks , alot less then if you fry something else
