Anybody know of a switched power source under the hood?

[M3V8Driver]

I orginally posted this in the track section, but never got a response:
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Just wondering if anybody has hard-wired an AMB transponder. I have an E92 M3 that I am running Time Trials with, and was wondering where the best place is to hook up the positive and negative leads. Obviously, it should be switched, so that it isn't on when the iginition is off. Any help will be appreciated.
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Bascially, I just need a switched power source so that when the ignition is on, the transponder is too.

[camaross305]

Originally Posted by M3V8Driver

I orginally posted this in the track section, but never got a response:
--------------------
Just wondering if anybody has hard-wired an AMB transponder. I have an E92 M3 that I am running Time Trials with, and was wondering where the best place is to hook up the positive and negative leads. Obviously, it should be switched, so that it isn't on when the iginition is off. Any help will be appreciated.
--------------------
Bascially, I just need a switched power source so that when the ignition is on, the transponder is too.

You can use the psotive post and negative under the hood and use a relay and just tap into when you want it to turn on

[kmarei]

you can also get to the factory harness at the top left corner of the hood are (right below the wiper
inside that box is all the wiring
i believe the accesory wire is red with white stripe
that is only powered when the engine is on

[camaross305]

Originally Posted by kmarei

you can also get to the factory harness at the top left corner of the hood are (right below the wiper
inside that box is all the wiring
i believe the accesory wire is red with white stripe
that is only powered when the engine is on

You could do that but be careful which wire you tap....

[kmarei]

i'd test first
you need one that reads 14.4v when the engine is on
there was a threat on e90 post with someone who fed 14v to the DRL bulbs that way
but i can't find it now

[M3V8Driver]

Thanks guys. I thought about using the positive post, but the hassle of trying to find an adequate switch and how to mount it turned me off (no pun intended). The switch would have to be able to take heat, vibration, and max amps (30?). Radio Shcak doesn't carry such a switch. So that's why I'm really sticking to the switched power source. I'll have to take a look in that box and test some of the wires. In the meantime, I welcome more feedback. Thanks again!

[kmarei]

found the link
here you go
http://www.e90post.com/forums/showth...light=red+wire

[M3V8Driver]

Originally Posted by kmarei

found the link
here you go
http://www.e90post.com/forums/showth...light=red+wire

Thanks for the link. So it looks like all I need to do is tap into the red wire with the white stripe to power the AMB transponder, so that it is on whenver my car is on, and off whenever the ignition is off, which is a good thing since the car ma sit a week without driving. Anyhow, what the heck are "angel eyes"?

[kmarei]

Originally Posted by M3V8Driver

Thanks for the link. So it looks like all I need to do is tap into the red wire with the white stripe to power the AMB transponder, so that it is on whenver my car is on, and off whenever the ignition is off, which is a good thing since the car ma sit a week without driving. Anyhow, what the heck are "angel eyes"?

it's the 2 circles in the headlights that are used as DRL
they are called Corona rings by BMW

[SS32]

30 amps? Holy shit, that thing sucks some power.

[kmarei]

M3V8driver
i sent you a PM
i need your help!!

[ff1600]

Assuming this what you are installing, the current draw is only 40mA. You could leave this on for weeks without driving the car and not hurt anything (using the oem battery). Just put a simple in-line spade connector (or inexpensive rocker switch) in the ground wire and disconnect it after your track day is over. 12v power from the jumper connection, inline fuse. No mods to oem wiring necessary.

Of course you will need to remember to reconnect it but that is what pre-event check lists are for.

[M3V8Driver]

Yes, I know the transponder draws very little amperage... I meant that if I were to install a switch, that it should probably be rated at the max amprage, ala fusebox, so as to ensure reliability of the switch. That's all. After giving this some thought, I decied that splicing into a wire in the factory harness is not a good idea, as I'm certain it's a sure-fire way to void the warranty, so if there is not a suitable switched area to attach an electrical connector, then I'll just crimp and two-prong connector on the end of the power lead and connect/disconnect as needed. Shouldn't be too much trouble to loosen the bolt by the positive jumping terminal and slide it in and retighten. Thanks.