Audio Systems: Sond system on Windstar 2001, koss cd player, speekers

Question
I tried to change de tape radio in a Windstar 2001 for a Koss CD player. I have the wire set that fit Ford original plug and standard wire color that i match whit Koss wire.  When i finish all the connection, the radio is on, but there is no sond! If i plug a speaker I had home (else than those of the mini van) it works, but if I plug the cd player whit the minivan speeker, no sound is made.  I tried to plug a 9V battery on the van speekers, but no sound, and if I plug back the old tape radio, everithing plays well.  So I understand that the CD player works, and the speekers are good, but why do the cd player dont work whit the van speeker?

I hope you can help me!

Thank you

Roger

Answer
If your factory stereo was a "premium" stereo there would probably be an amplifier hidden somewhere that the factory stereo turns on and the new one doesnt turn on.  You can either rewire all the door speakers directly to your cd player or try to figure out which wire turn the amp on.  there is probably a wire that you can find in the factory harness that isnt in the stereo harness.  You could put a meter on this and see if it goes posative when the factory stereo is on but doesnt when the new one is on.  
Check it out and let me know.