Audio Systems: no sound, factory speakers, factory stereo

Question
I recently took a factory stereo out of a 91 Ford Escort and installed a working Cd stereo.Everything was wired correctly(wire harness) and it powers on and functions but there is no sound.
I took it up to Best Buy and they tested the stereo and it played on thier system.
Note: I reinstalled the factory stereo and the speakers work? ( the speakers are the factory speakers)
Best Buy suggested that it may be a short in the speakers which cuts the integrated amp out.?

Does thier suggestion sound accurate and how should I test them?

Thanks,
CRaig

Answer
many fords were available with premium sound systems that had a factory amplifier somewhere in the car.  if you look at the harness there may be a wire that isnt in use, or a wire that is in the factory portion of the harness but doesnt continue on with the one that you bought.  this may be the wire that triggers the factory amp to turn on.  Take a look at page 6 of this file:

http://www.installdr.com/InstallDocs/FLM/PDF/356013.pdf

it shows that there are 2 connectors, one black and one gray from the factory harness and the left most wire on the gray one is labeld as "I" and the decription below says "amplifier turn on"  if your's looks like that I'd say that's your wire.  you may be able to splice it to the blue remote wire comming from your new cd player to trigger the amp to turn on.

GOOD LUCK!! please let me know how it goes.