I bought the car used in 2003 with 113k miles. To this day it runs and looks immaculate. However, the stereo has a power amp under the passenger seat which I believe has a short in it. Since the day I bought it the radio has played through the passenger speakers only but once in a while all four would work briefly. Now the radio is beginning to cut in and out totally. My wife says when she sits on a hill or excelerates, it tends to work. My question to you…is this the pre-amp shorting out and if so, can this be removed and bypassed to regain sound back to the four speakers? I’m not concerned about the stero surround sound that the car is known for, it’s too old and would be too expensive to correct. But I would like to get basic radio reception.
I don’t think you have a shorting problem, it sounds more like a bad connection problem. The trouble may be with the external amp or with the head output. If the inputs to the external amp are RCA connectors you could try reversing the front and back leads and see if the trouble changes also. If it dosen’t then the amp is the trouble or the connections to the front speakers.
Check the balance control also to see if there is a problem with it. Try adjusting it to see if that changes things.