back up camera not working with z3

i put a pioneer z3 in a 2005 magnum. i hook up the back up camera and it really dark. so i plug the rca from the camera into the video in feed, and its perfect. i hook it up to a z2 in my car and it works fine on the reverse camera input as normal. so then i took the harness from mine that has the reverse camera input that i know works fine and switched it with the z3 and i still have the same problem. cant fiqure it out and the car has to leave saturday. could the headunit be bad?

yes i originally had it hooked up the the (+) reverse signal from my headunit harness. but im still having the problem after i disconnect it and hook up both the positive from the camera box and the reverse wire to a battery charger. and yes my headunit is in the positive polarity mode.

go to the setting of the monitor then system setting you can see ntsc, pal, or secam, since you are in the united states the system there is ntsc, so select ntsc.FrAncIscO