12v Constant, Switched, and adding peripherals..

[Cheetah]

I just picked up a new (to me..) 84 BMW when I got home from deployment, and I'm just digging my nails into it finally. First issue is that the stereo doesn't hold presets when the car is turned off, and every time I start the car I have to manually power on the stereo, which ejects any cd in it. Pain in the ***, my first guess is that for some reason there's no constant 12v running to the HU...I'll come back to this.

Next, there's a very retro radar detector wired up, it seems to be using a power cord from a floor lamp haha. Unfortunately I'm unable to trace the wires to their source as they run too deep into the dash, even after ripping out the instrument cluster I can only get so far along them before they get buried. I'm thinking my power for my HU may be going to that, but at the same time, it won't power on while the car's off, so I second guess myself...Either way, any ideas how I can figure out what the three wires running to the unit are with the only accessible end being soldered to the PCB inside the thing?

Last piece of information, I'm trying to throw in an HD radio receiver, easy enough to wire up, save the lack of a constant 12v source. This is where the actual questions come in, thanks for bearing with me this far.

The only constant 12v I know how to get my hands on is my lighter at the moment. Either A) How do I dig out the power that's supposed to be going to my HU, possible alternate locations it's been routed? or B) If I pull the wire from my lighter and route it to my HU, the lighter (used to power a GPS) and an HD radio tuner...Seems likely to blow a fuse to me?

I pretty much just ripped out my entire dash to dive into electrical work, with no experience beyond wiring up aftermarket HU's, speakers, and amps on a simple level...Nothing requiring extreme modification or finding wires from another area of the car..

Summary question: Where in the name of Satan's fiery anus do I source my constant 12v, as well as the switched 12v to power peripherals such as an HD radio, possibly satellite radio in the near future, and anything else that would need a switched source for power?

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[MitchZ 10+ year member]

I've never had a 84 BMW before but you may want to get a wiring harness if they're availiable for your car.

Remember to check the fuse box before digging through the mess because thats where everything in the dash goes through. Then your best bet would be to dive in with a DMM.

Or you could google search wiring diagrams for your car.

the12volt.com has some good stuff as well - it might just have the diagrams for your Beamer

 

[SethPhillips 5,000+ posts]

the headunit is wired azz backwords.. duh..

the constant and switched are hooke up backwords..

as far as getting a new constant, and switched. i would check all fuses and rewire it at the factory harness behind the deck.

if not go to the ignition harness and be sure to fuse ur wire's..

honestly i would take it to someone who know's what they are doing and they can rewire it so that youre car is not a fire hazerd

 

[Cheetah]

Wiring harness is a no-go, factory one was cut off sometime in the past and a generic brand cd player's harness crimped to the factory wires, no wiring diagram for the HU.

I grabbed the wiring diagram for the car off the12volt.com, my biggest concern is that it's cool if I just splice the 12v to run the HU and the radio?

Taking it in would be my first choice, but I'm short on cash. Apparently the government was kind enough to overpay me while I was in Iraq, and now they want their money back...Thus why I'm ripping my car apart in a parking garage instead of going out and doing something with my time..//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[mokedaddy 5,000+ posts]

Yes you should have no problem using the constant and switched for both the headunit and hd radio piece.

But make sure you test the wires with a test light or dmm and dont just go by whats listed on 12v. They are usually right but not always.

 

[SethPhillips 5,000+ posts]

Wiring harness is a no-go, factory one was cut off sometime in the past and a generic brand cd player's harness crimped to the factory wires, no wiring diagram for the HU.
I grabbed the wiring diagram for the car off the12volt.com, my biggest concern is that it's cool if I just splice the 12v to run the HU and the radio?

Taking it in would be my first choice, but I'm short on cash. Apparently the government was kind enough to overpay me while I was in Iraq, and now they want their money back...Thus why I'm ripping my car apart in a parking garage instead of going out and doing something with my time..//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

my good friend is pissed at that army shit.. he said they want to take money away from him allso! i think it's bullshit!

 

[jrwalte 10+ year member]

You can always route your own 12v source from the battery. Just use a 12 or 10g wire and run it through your firewall grommet where your existing wires run.

 

[Cheetah]

Wired it up at the HU, it's a messed up head...For some reason the switched and the ground both have two wires running into the HU, where they crimped onto the car's wiring they threw in two wires from the HU's ground and 12v going into it. Anyway, radio works, save the fact that the manual sucked hard and didn't really explain the hookup all that well, so for now I'm just using it as an extension on my FM antenna //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

I had planned on picking up a new HU soon, but this may have expedited the process a little, as well as ripping out the fader knob that's wired into the dash from the factory because the stock radio only had outs for one set of speakers, which went to a fader and split it front and rear..Annoying.

 

[dman4486 5,000+ posts]

Wired it up at the HU, it's a messed up head...For some reason the switched and the ground both have two wires running into the HU, where they crimped onto the car's wiring they threw in two wires from the HU's ground and 12v going into it. Anyway, radio works, save the fact that the manual sucked hard and didn't really explain the hookup all that well, so for now I'm just using it as an extension on my FM antenna //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
I had planned on picking up a new HU soon, but this may have expedited the process a little, as well as ripping out the fader knob that's wired into the dash from the factory because the stock radio only had outs for one set of speakers, which went to a fader and split it front and rear..Annoying.

my mav had that same crap