1999 Dodge Ram 1500 stereo

My friend has a 1999 Dodge Ram 1500.  His Stereo was stolen on Easter Sunday and he went to go get a new head unit.  He got a sony head unit to replace he factory and installed it.  At first when he played the raido his front speakers worked but not when he played the CD.  Well he sent it to Sony and Sony sent him a new head unit.  Well same thing happend then about a week later he didnt have any front speakers at all.  We swapped the front speakers with the back ones and they worked fine so I know he dosnt have blown speakers.  And yes we tried putting the fade all the way forward.  The Only thing that I saw out of the ordinary was a black wire with a blue strip in the same wire bundle that is with his stero wire bundle that dosnt go to anything we tried putting it to ground but nothing happend on the wire schematic through this site there is no listing for a black wire with a blue stripe.  I guess my question is has any one heard of this and if so how did you fix it to get the front speakers to work.  Thanks for your time and please let me know anything I might have forgotten

Mike

well all connections are good there is good continuity from the deck to the speakers.  He said he has the infinity sound system in it when they jacked his stock stereo and there is a amp or something that should be in the dash but its missing could this be the problem or were else should we look for problems.  he tried hot wiring the speker directlly to the head unit but still no workie.  Thanks again for all the help.

Mike