I need the wiring diagram for the radio. It is not turning on and I have an extra red wire left. I don't know what that wire is. I already have:

white/red going to constant 12
yello/red going to ignition 12v

don't know what the red one goes to and I don't have any blown fuses and very good ground down to bare metal. Am I supposed to mate that red wire with the ignition wire on the harness?

Thanks

I you are taking about a Honda/Acura and the stock radio wiring harness the red is the illumination ground, it comes from the "Dash Light Brightness Controller".
The dash lights brightness, on Honda/Acura, is controlled by continuity to ground, the "DLBC" is a variable resister, dash light, [illumination] power is red/black and the ground is red.
Your aftermarket HU will not need either the red/black, [unless it has an orange lead] or the red, cap them off so they can not short out, DO NOT connect them to any other leads.

You have either miswired something or a blown fuse...
http://www.installdr.com/Harnesses/HA-Wiring.pdf 94

You get what you pay for.

Nothing is impossible, the impossible takes longer and costs more money.

Thanks again :-D

You get what you pay for.

Nothing is impossible, the impossible takes longer and costs more money.