Audio Systems: No sound from cd player, ford mustang, new radio

Question
I just purchased a 1993 ford mustang. The stereo was missing and I bought one to replace it. I hooked everything correctly the stereo works fine but no sound. I found a factory amp underneath the passenger front seat.I checked the connections to the amp. All connections are tight. Is it possible the amp is not working? I hooked up to a house speaker and it works fine. How do I know if the amp is bad?  

Answer
there is a blue or a blue/white wire on the new radio that needs to be use to turn on the factory amplifiers   there is no audio because they are off

i don't have the 93 only 94 and up
good luck

http://www.installdr.com/InstallDocs/FLM/Mustang.html