Hi all,
I am installing a back up camera into my 2005 Mustang GT and it says to run the 12v source to let it know when the transmission is in reverse to the reverse switch. I ran it through the transmission shifter hole and am trying to tie it into the reverse light switch on the transmission. However, I can't seem to get any voltage when it is all connected.
When I unplug it, the side with the purple wire has 12v (constant on?), but when I plug it in and put it into reverse, the other side, which I assume would be switched on, only has like 0.05 or 0.1v.

How does this switch work?

Is there something I'm missing? Or is there another wire up front that has 12v when the transmission is put into reverse? I'd rather avoid running a wire all the way through the cab to the very back of the vehicle for the reverse light if I can help it.
Thanks.

 

Here's the diagram for ya:

https://iihs.net/fsm/?d=40&f=Reversing%20Lamps.pdf

As you can see, the thing doesn't exactly get the 12v signal from the battery, but through all this other stuff. The CANBUS is... weird. Ford does some strange things with their sensors/switches, none are direct connected, but go through computers, which causes... this.

I'd get the signal from the reverse lamp. Just the way these computer cars are these days.

 

Thanks for the info houtex, I was wondering if it was something like that.
I remember running into that on my 85 Bronco with the taillights and cruise control, activating them actually grounded it out and made the voltage go to 0. Or something along those lines.

Either way, was hoping to not have to run it to the back since I already finished routing the camera wire and pulled the whole car apart, and finished buttoning it up and back together. lol
But if that's how it is, then so be it. Wasn't too bad.

Unless anyone knows where that wire might be up front? I imagine the signal to the back up lights starts from the front where the computer is and goes to the back, so it'd be nice to tie into it there.

 

It's in a bundle running in the sill... honestly, I'd run the wire, but if you must... here ya go:
https://iihs.net/fsm/?d=40&f=Compone...Views.pdf&p=11
Harness from SJB to the rear, going down the sill plate to...
https://iihs.net/fsm/?d=40&f=Compone...Views.pdf&p=15
The harness continues and then you hit the reverse lamp.

Left side is similar. But I think I'd do the right side because SJB that side. Either side, you can take the sill plate off and open up the bundle and find the wire in there, or you can take the kick panel off and figure that out, or on the right side get to the actual pin of the SJB and get it in there (I wouldn't)... Even get all up under and in that dash and find it in the crossover harness. All kinds of possibilities!

Again, good dang luck!

 

That's what I was thinking too. When I put a backup camera in my truck I tapped the reverse light wire in the driver's side foot well.

BTW, I have no idea why the shop manual is out there for free, but I'm gonna cry if they ever take it down. I'm amazed you can see C2280D on the wiring diagram, and then look at the component view and see which harness that's in. Of course, looks like it merges in right away into the bigger bundle so it'll be a matter of unwrapping it at a convenient place and hope the color codes are easy enough to pick out.

 

Thanks again for the links to the wiring diagrams. Much appreciated!

I decided the best route was to simply run it to the back. I'd have to pull the side panels apart and find the wire, which would be no different really than taking off the center console again and popping out the back seat and running it to the trunk.
I'd already done the latter once so I knew how it all came apart, and honestly, the Mustang interior disassembles easier than almost any other vehicle I've worked on. I was impressed. I think I had the wire to the taillight in about 20 minutes.
It's hooked up and working now.