1995 T & C need stereo wiring help!
 

I have a 1995 Chrysler Town & Country mini-van that I am replacing the factory Infinity stereo with an aftermarket Kenwood unit. I bought the wiring harness adapter from a car audio place and the mounting face plate thing. I hooked up the speaker and power wires and still have three wires left. One is from a small thin plug on the back of the Infinity unit that has a white/black striped wire and a purple wire (2 pin connector). I also have the single dark greenish wire with the stripe that has a black plastic connector. When I wired up the single dark wire from the small single wire connector to the power control wire on the new harness the back speakers were barely working. What have I done wrong? I would appreciate any help as I gave this van to my 16 year old son a few months back and got him the new stereo for Christmas as the Infinity was on its last leg. Help me please! Thank you!