No-Pistons-TT

Ok now this is odd when i turn my speakers on audio only plays out of the left driver side of the car. But if i change the balance all the way to the right it will play out of there???? but very quietly but enough so i can tell both speakers are working. I still have the stock head unit in and i really dont want to go buy a deck because i know i will spend to much on one any suggestions?? I have a 94 rx-7 none-bose.