Audio Systems: chrysler infinity stereo replacement, stereo cd, service manuals

Question
I have a '94 T/C that had the infinity stereo cd deck in it.  When that died, I just put another simpler chrysler radio in until I bought something else.  Well, that radio plugged right in and all 6 speakers worked fine.  Now a friend gave me a Jensen 4x40W car stereo that he had in his Chrysler, so the harness work was already done.  Thing is, when I plugged it in, the front speakers work fine, but the side and back you can barely hear anything.  I thought the amp for the back speakers was bad.  But, I tried running the front two speakers off the back speaker connections in the stereo, and they fired right up.  Can't for the life of me figure out why the cheaper chrysler radio would make the speakers work, but not this Jensen that was wired in another chrysler van.  Something w/ the fact that it was an Infinity?  Or some grounding problem?  

Answer
Jim,
Please give me the model number of both of the Chrysler stereos. I will look over the service manuals to see what type of outputs they have on them and let you know. With the Jensen stereo the wires may not be connected the same as what is needed in your vehicle. The problem may be that you vehicle has and external amp installed.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net