Can anyone tell me weather or not the 94 Trooper has an on board amp and if it does where is it located. The only way I can hear any sound from the speakers is to turn it wide open and put your ear to the speaker.

maybe the speakers are all blown

Hi, I have a 94 with the cd system, and there is no external amplifier in it. I had to replace the speakers when I bought it, used , as they were shot. later, I replaced the radio with aftermarket, and it worked out great. The stock radio started losing channels intermittently and I just got tired of messing with it, so out it went.
Good luck

The headunit is the amp. It may be blown. If it's all four speakers, it's likely that that is it, or it's a fuse on the player somewhere.