I have a 97 lariat with the stock head unit. Ever since I bought the truck, the left rear speaker doesn't work. I can turn the balance and fade to that particular speaker, and if I turn the radio WIDE OPEN, I can hear some sound out of it. I thought it was a bad speaker, so I replaced it with a new one. It didn't fix it. I recently replaced the on/off switch on my radio with a new one, and when I did, I started manually jumping wires from the head unit into the output wires. I could get the left rear speaker to work, by crossing its wire to another post on the head unit. So, I came to the conclusion that the head unit is bad. I checked it for the obvious, (broke solder joints/board cracks) but I didn't find anything. I would appreciate any suggestions as to how to fix the head unit. I know my way around a multitester, but there are a lot of wires coming out of the back of the head unit. Thanks in advance!

 

My first guess would would be that the HU actually has a bad channel. Not a bad connection, but bad electronics. Not to be pesimistic, but in my life I've had plenty of audio gear loose a channel...

 

Does anyone have a pinout on the back of the stock radio. Which pins do what? On the sound output clip...... Thanks...