Problem with Accessory Wire - Head Unit Install

[Jutzi420]

Now, this isn't for my MX-3 but I'm hoping someone might have some insight. I'm taking my old headunit from my car and putting it in my work van, a 2004 GMC Savanna. I've got all the speakers wired proper and I've got three wires left over, I got my constant 12v from the battery, my ground, and the last should be my accessory. The problem is when I turn the key the accessory wire just spikes to about 8-10 volts and goes back to nothin, I've never had this happen before, every other vehicle I've wired gives a constant 12v on the acc when the key is on. Anyone got any ideas what could be going on? Thanks.

[Nd4SpdSe]

im guessing either the deck has aux turned off, or there's a short and its protecting itself

[hondah8er13]

sounds like that is your power antenna wire... my maxima has a power antenna and that wire will give some power just long enough to put it up then stop and when you turn off your key it will do the same to bring it down.. just a thought

[Jutzi420]

Nope, no power antenna. I found a few posts on the subject. I'm still a little lost on exactly how it works, but GM made it real difficult to put in an aftermarket deck in 2002+ vehicles. You either have to retain your factory deck and run your aftermarket through it, or buy an interface which will allow your new deck to perform the extra functions that the standard one handles.

Here's the best post on the subject I've found so far: http://forum.sounddomain.com/forum/ultimatebb.cgi?ubb=get_topic;f=3;t=020461

And here are some links to some of the different interfaces: http://www.crutchfield.com/S-7tE9nDSMX6l/cgi-bin/ProdView.asp?a=&s=0&cc=01&g=751&id=detailed_info&i=120GMRC01
http://www.autosoundgear.com/tek9.asp?pg=products&specific=jpfnisd0

Oh yeah, GM also decided that the standard antenna plug size was too big and uses smaller ones. So you also gotta get an adapter to switch it back up to standard size. What'll the geniuses over there think of next?

[drift]

You should try wiring the accessory wire to your ingition, or even splice it with the constant 12v. You'd have to make sure you turn it off when ever you get out of the car, but it would be better than having to run it through your stock unit.

[Typhoonk]

Stereos in those GM cars (about 2000 and up depending on which vehicle you have) have the databus system.
Which to my knowledge is kinda like using the radio as a memory bank,and to save some things or control some other things (ex. the ding when you leave the keys in the ignition).
I don't know about that black box thing. Because whenever I've seen a 2002 cavalier with the system- and the car has a bad radio that needs replacing - the dealer has to program it with something for that specific vehicle.
Untill that black box thing gets more "experience", I'm gonna stick to relocating the radio (the radio that was made for the car).
And if you really want the radio to stay on for a bit after you remove the key check this out: (click on -> Radio On Until Door Opened)
http://www.the12volt.com/relays/page5.asp#drto

[Jutzi420]

Well, I picked up metra's black box. I had to part with a pretty fad wad outta my wally, but it was worth it. It's about as easy as using a harness adapter and retains all the OEM functions. I don't think it works with OnStar though, no problem with that though cause I don't got it, I think there's another box out there that'll handle the onstar as well.