I had this same problem. After reading other ideas and some trial and error, I finally got it. Most Caravans have an Infinity system (the speaker grill will say Infinity on it) ,which uses an amplifier to run the door and rear speakers. I had to ground the clip wire that was originally attatched to the strap ground on the factory installed radio. Then I also had to hook the wire on the new radio for power antenae (blue and white on my unit) to a blue wire on my new harness. This wire came from the last wire of 7 wire harness that had the other 6 wires for speakers. The original wire appeared to be green/red on my vehicle. After I connected both, the speakers cameon and sound great again.