After adding a headphone jack to my dash for my Premier (Pioneer) aftermarket stereo, my buddy now wants the same on his 2 cars.

1) He has a Chrysler Concorde 1994 with factory stereo. However, I have a 2002 Chrysler CD player (RBK) that supports (and comes with) the CD changer. I have the schematic and I know on the CD changer port what the wires are for sound input (left, right, gnd). However, I tested it and I can't switch to the CD changer input; the head unit doesn't see that it's on. There are a cople of more wires (dimmer, J1850, and another one). Anyone know what I need to do to make the head unit think the cd changer is always plugged in?

2) His main car is a Honda Prelude 2000 Vtec. Factory radio. Anyone know if this supports a CD changer / AUX input? I'd like to help him out on both cars.

I've done searches on this forum and haven't been able to find anything on either topic.

Thanks in advance
M