1995 lexus es300 audio problem
 

Okay my dad bought me an es300 for christmas. I love it. Its awesome. It rides good and it runs good.. its got 194,000 miles on it and everything works.... except the radio. Sorta. I only have sound coming out of the left rear speaker. The rest are silent. I took the amp out and took it apart and cleaned it and put it back in and no luck still the same results. But if I turn the fader to the front and then turn the volume all the way up , I can hear the radio just a little from the from speakers. So I'm not sure what's wrong with it. Any help is much appreciated. Thanks!