I have made a harness to plug a '00 Civic Si head unit into an older EG. I am left with 2 wires on the '00 harness... a red wire, and a red/black wire. Which one do I connect to the orange dimmer wire on the aftermarket side of the harness? According to the Haynes manual, the two wires come into a } and says "Interior Lights"

I'm not sure if I'm supposed to combine the 2 wires or leave one of them hanging. Most sites are saying that the red/black is the one to use for the dimmer / illuminator

So will I be leaving the red wire hanging on the OEM side, and the remote (blue) wire hanging on the aftermarket side? I don't want to make a costly mistake...

 

The red/black is the illumination, [it would go to the orange lead] however the HU illumination lights will not work unless you ground the red lead, or connect it to the red lead at your "Dash Light Brightness Controller", [also called a dimmer].
In Honda/Acura the dash lights ground is controlled to dim or brighten the dash lights red/black is 12V+, [hot when park/head lights are on] red is ground, [from the "DLBC". 94

 

can i tie the red wire in with the black wire then?

 

Any ground should work. 94

 

thanks a billion! that black wire is conveniently next to the red, i'll see how it works out