Idiotically shorted my car, need help

[Staszek]

So, I installed my new stereo a few weeks ago, but for some reason the sub was not working.

I tried a few things, first I hooked my iphone directly to it (its powered) and it came alive. I was thinking ok maybe its the RCA cables, so I ran a new one outside the car directly to the head unit, no dice. I played with every single setting on my Pioneer DEH-8700BS turned the sub on and off, played with the settings for the cross over nothing.

So at this point I am thinking there is something wrong with the head unit. I have an old Eclipse head unit that the car came with I figured I would hook it up really quick to see if it ran fine with the other headunit.

Here is where I F'd up, completely my fault. I should have disconnected the battery but I was working quick and stupid.

As I had the 12v constant loose (the old radio was already grounded) the constant hit the chassis of the radio.

All the sudden the doors locked and alarm beeped. Nothing else no spark etc.

Well now the car is messed up. It starts and drives no problem. Oddly the central lock works sometimes, but I have no dome lights, no check control, no power to the radio (either one old or new). The OBC lights up when you start the car but there is nothing on the screen.

I checked all the fuses, nothing went, I changed them anyway. I am assuming that the light control module is shot, but would that mess up the OBC and the check control?

Not sure if my alarm is now shot and the lock control module as well.

What do you think?

[Staszek]

Anyone?

[Staszek]

No one has any suggestions? I plan on replacing the light module and the alarm brain this weekend just in case. Also have a new lock module. Still not sure why the radio won't power though.

[Das Delfin]

I suppose you would want to pick up a manual with a full set of wiring diagrams and map out each circuit to see how they are connected. You could start by tracing the source of 12v constant for the radio and then also the ground for the radio and see if either of those are connected to your OBC and central locking in some way

Then I would make sure the fuses for each of these circuits are the correct value. I know you already changed them but make sure they're correct just in case

It sounds kinda like a fuse 21 problem. Each of those systems are powered by multiple fuses. Get the fuse box diagram which shows which fuses control each circuit and then pull each fuse and see if there's continuity across their leads in the fuse box.

I have seen electrical wire burn up with enough current when shorted. Not sure if yours had contact long enough to do this, but it doesn't take too long. It's possible the 12v or ground wire for your radio has been disrupted. Grab a multimeter and test for voltage between those two wires. And then also your 12v switched line.

Lastly, you want to make sure your 12v supplies for the radio are original. It's easy to grab a 12v from another source under the dash so take a look at the color code and match it with the wiring diagram. This will help isolate the radio circuit

Usually bmw diagrams use color codes which are abbreviated in German so you'll want to learn the colors. You already know black, red, and green :P

[Staszek]

I suppose you would want to pick up a manual with a full set of wiring diagrams and map out each circuit to see how they are connected. You could start by tracing the source of 12v constant for the radio and then also the ground for the radio and see if either of those are connected to your OBC and central locking in some way

Then I would make sure the fuses for each of these circuits are the correct value. I know you already changed them but make sure they're correct just in case

It sounds kinda like a fuse 21 problem. Each of those systems are powered by multiple fuses. Get the fuse box diagram which shows which fuses control each circuit and then pull each fuse and see if there's continuity across their leads in the fuse box.

I have seen electrical wire burn up with enough current when shorted. Not sure if yours had contact long enough to do this, but it doesn't take too long. It's possible the 12v or ground wire for your radio has been disrupted. Grab a multimeter and test for voltage between those two wires. And then also your 12v switched line.

Lastly, you want to make sure your 12v supplies for the radio are original. It's easy to grab a 12v from another source under the dash so take a look at the color code and match it with the wiring diagram. This will help isolate the radio circuit

Usually bmw diagrams use color codes which are abbreviated in German so you'll want to learn the colors. You already know black, red, and green :P

I have one, I used it to get the car back into shape when I bought it, the PO cut a bunch of wires, when I bought the car half the stuff didnt work.

I will have to test the twelve volt supply this weekend. I was using the original radio ground, I have the color and wiring diagram and it was all working. I hope I didnt burn up the wires. It only touch for a second, I am so pissed at myself, I always disconnect the battery :(

Fuse 21 was the first one I replaced, I will check it again. I hope I don't have to start tracing a bunch of wires.

[Andy.B]

Have you checked continuity across the fuses? I have seen some blow but only with a hairline crack nearly impossible to see with the eye.

[Staszek]

Have you checked continuity across the fuses? I have seen some blow but only with a hairline crack nearly impossible to see with the eye.

I will check, I replaced the fuses with new ones. But maybe those were bad, I will have to look.

[Cephas]

You've had some seriously ridiculous electrical problems with this car. I'd say this is one as well. My thoughts are that you somehow burned out the alarm system brain. Do all the lights run through it as well? Does the alarm share a ground with the headunit?

Edit: that doesn't really account for the check panel and the OBC though. Not sure on those two. The only think I can think is that the radio ground was being shared by other components and when you shorted the 12v constant it made its way through those components as well and toasted them. It could also be that they share a ground and that wire got toasted. That actually makes the most sense to me.

[Staszek]

You've had some seriously ridiculous electrical problems with this car. I'd say this is one as well. My thoughts are that you somehow burned out the alarm system brain. Do all the lights run through it as well? Does the alarm share a ground with the headunit?

Edit: that doesn't really account for the check panel and the OBC though. Not sure on those two. The only think I can think is that the radio ground was being shared by other components and when you shorted the 12v constant it made its way through those components as well and toasted them. It could also be that they share a ground and that wire got toasted. That actually makes the most sense to me.

Yea, the PO messed up so many things, and I had all of them fixed, and then by being stupid I messed it up. Well I got a new alarm brain and Light control and lock control. I will check the ground, does anyone know where the radio grounds too?

[Das Delfin]

Your wiring diagram should tell you the name of the grounding point

[Staszek]

Your wiring diagram should tell you the name of the grounding point

Haha I have read so many colors I never really looked at grounding locations on that diagram.

[Staszek]

Got it!! The worse part is I am not 100% sure what it was. So I am pretty sure it was a combination of things, Fuse 21, which I replaced again with a brand new one, although when I pulled the old one I accidentally dropped it into the engine bay somewhere, I guess I will find it when I pull the engine, Im not sure if it was really blown or not.

I changed the Light Control Module, had an extra one, then I replaced the alarm brain because I think that was fried, it was lock the doors on its own.

Once I did all that I hooked up the power again and everything light up an worked like its supposed too. My sub still doesnt work correctly, but at least my dome lights, OBC, locks and radio work again.

[george graves]

Light Control Module? You mean the interior lights? Or the head light switch? I blew out a headlight switch when I let the dash illumination wire short to ground once. Whoops - it happens.

[Staszek]

Light Control Module? You mean the interior lights? Or the head light switch? I blew out a headlight switch when I let the dash illumination wire short to ground once. Whoops - it happens.

Interior lights. I actually blew the dimmer one I bought from you, but I had the OEM one still. I almost sold it.

[george graves]

Hmmm. That's odd. Return it and I'll fix it for the parts cost and return postage. Won't be more then $5 I would assume.