Test lights cost about $5. Ground it and unhook your radio from the power socket. Turn on your lights. Push the point into each one of the connections. When your testing light comes on play with the dimmer. If the light dims, you have found the dimmer wire!
I went to a junk yard and cut my clock adapter out. I was going to use a USB cable connector but opted not to.
This was the first mod I did!
-Andy
