i got the headunit but can't figure out on how to wire up the auto dim wire (orange/white) where does it go? i can't find where it gets tapped into.. someone help

 

i foudn this awhile back, i think its what you want. not positive tho
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If you notice, the orange wire of the "factory harness" you bought does not connect to anything on the other side. This was bugging me for a long time to and someone else helped me out. In order to get the dim function to work, you actually have to connect the orange-white wire from your headunit to a different wire on a different harness entirely. I will try to find it and post it here for you. But yeah, I know that is your problem.
Ok, so it is the Red wire with a blue stripe that you need to look for. It is located on one of the other harnesses. I am not positive which one it is, but there is only only red/blue wire on the 4 harness connections, so just look for it. Attach your illumination wire from your radio to that one and you should get the dimming function to work.

Hope that helps.
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worth a shot, but id see what others say

 

On the Metra 70-7550 and 70-7551, it's the orange wire. Connect it to the orange/white wire on the Pioneer 4300DVD's wiring harness.

It's on the standard aftermarket wiring harness, not on any of the others. The only wires you have to connect to that aren't there on the standard harness are the ones for the steering wheel controls and the vehicle speed sensor wire.

 

i did connect the orange/white wire to the harness but it doesn't do anything.. so i think i have to tap it into the wire that hdmark was talking about..

 

The orange wire on the Metra 70-7550 or 70-7551 is already connected to the red wire with a blue stripe from the factory radio harness that it plugs into.

If you're using some other brand harness, there's a chance that the orange wire isn't mapped the same as metra does it.