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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > Rear View Mirror 12v Ignition Supply



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      11-05-2013, 01:21 PM   #1
Scottfreee3
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Rear View Mirror 12v Ignition Supply

Hi,

I was attempting to wire in a dashcam to the rear view mirror. I have this done to my E46 but I cannot get a 12v from the green/white wire which as far as I know is the 12v ignition supply.

Can anyone shed some light on this? I have attached a photo of the wires I have.

I was going negative to Brown/Black and positive to Green/White. Is this right?



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      11-05-2013, 02:18 PM   #2
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This thread might help

http://www.e90post.com/forums/showthread.php?t=25207
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      11-05-2013, 02:33 PM   #3
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Be careful about simply tapping in to an existing wire to power the cam. The current draw of the camera is going to be significant and you may end up overloading the circuit you are tapping. I strongly suggest tapping in to the fuse panel behind the glove box with an add-a-fuse and running the wires up the A pillar to the mirror area.
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      11-05-2013, 04:30 PM   #4
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Quote:
Originally Posted by jwzimm View Post
Be careful about simply tapping in to an existing wire to power the cam. The current draw of the camera is going to be significant and you may end up overloading the circuit you are tapping. I strongly suggest tapping in to the fuse panel behind the glove box with an add-a-fuse and running the wires up the A pillar to the mirror area.
I agree it does add load however I want dont want to install the wire down thee A-pillor. If I cant get it working I will go down this route.
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      11-05-2013, 06:38 PM   #5
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Quote:
Originally Posted by jwzimm View Post
Be careful about simply tapping in to an existing wire to power the cam. The current draw of the camera is going to be significant and you may end up overloading the circuit you are tapping. I strongly suggest tapping in to the fuse panel behind the glove box with an add-a-fuse and running the wires up the A pillar to the mirror area.
That's what relays are for.
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      11-05-2013, 10:27 PM   #6
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Quote:
Originally Posted by Scottfreee3 View Post
I agree it does add load however I want dont want to install the wire down thee A-pillor. If I cant get it working I will go down this route.
It is honestly extremely easy though. If you pop off the little SRS sign cover there is a Torx bolt behind it. Take that loose and the whole A pillar cover comes off. You can then chase a wire down through the dash with a wire fish and into the glove box. If you have newer car there is a cigarette lighter outlet pointing down next to the glove box that you can plug the cam into and that is switched with the ignition already.

I seriously advise against tapping into the mirror wires without using a relay. The wires themselves are not sized for the additional current draw of the cam and neither is the fuse that feeds them. You risk either blowing the fuse often or even overheating and melting/burning the wiring. Flaming death is certainly not advisable.
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      11-06-2013, 12:33 AM   #7
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Quote:
Originally Posted by bmw325i View Post
That's what relays are for.
A relay wouldn't get you out of needing to run another power wire up the A pillar if you don't want to piggyback on the mirror supply.

Quote:
Originally Posted by jwzimm View Post
The wires themselves are not sized for the additional current draw of the cam and neither is the fuse that feeds them. You risk either blowing the fuse often or even overheating and melting/burning the wiring.
First part's certainly true, but you'd need to be pulling PILES AND PILES of current before you run the risk of fire. Tens of amps additional, which the camera won't.

Even still, nobody wants to change a fuse a bunch of times when you don't need to.
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      11-06-2013, 12:53 AM   #8
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Quote:
Originally Posted by alexwhittemore
Quote:
Originally Posted by bmw325i View Post
That's what relays are for.
A relay wouldn't get you out of needing to run another power wire up the A pillar if you don't want to piggyback on the mirror supply.

Quote:
Originally Posted by jwzimm View Post
The wires themselves are not sized for the additional current draw of the cam and neither is the fuse that feeds them. You risk either blowing the fuse often or even overheating and melting/burning the wiring.
First part's certainly true, but you'd need to be pulling PILES AND PILES of current before you run the risk of fire. Tens of amps additional, which the camera won't.

Even still, nobody wants to change a fuse a bunch of times when you don't need to.
Okay. So I was being a little dramatic on the flaming death comment. It is still a bad idea to try and pull power for the cam through the stock wires up there.
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      11-06-2013, 01:22 PM   #9
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I will run a cable down the A piller and into the fuse box. The car is a 2006 so hopefully it will have a cig connection in the glove box.

I have had the dash cam in the e46 for well over a year now and seems to be working ok. However I would like to put a relay into it but if its working away I dont fancy going near it
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      11-06-2013, 01:28 PM   #10
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Quote:
Originally Posted by jwzimm View Post
Okay. So I was being a little dramatic on the flaming death comment. It is still a bad idea to try and pull power for the cam through the stock wires up there.
Honestly it's probably not even a problem, but on the principal of "do it right the first time" it's virtually no additional effort to pull the A pillar trim. Might as well.

Quote:
Originally Posted by Scottfreee3 View Post
I will run a cable down the A piller and into the fuse box. The car is a 2006 so hopefully it will have a cig connection in the glove box.
Even if it doesn't, you can just pick up a $5 socket at radioshack or fry's (if you have one) and feed it with a fuse tap.
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      11-06-2013, 01:48 PM   #11
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would strongly agree with others, wire from the fuse box up to the mirror. Very easy to do and you don't risk damaging the existing wiring!
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