Right side speakers not working - solved

Hey guys, I was driving the other night (trying to beat my fuel light to the gas station, long story) going around a corner and suddenly the music volume dropped significantly only to quickly realize my right side speakers had stopped working. I have an aftermarket head unit, so I assumed that somehow BOTH right side speaker wires maybe came loose or that the stereo had finally given up on life. So tonight after work I tore into it. I didn't see anything wrong with the wires, so I ripped the stereo from my '85 Toyota Pickup (same exact head unit actually) and swapped it. Anyways, bottom line is I had the same results. I did however find out that the right side speakers were in fact working, but so quietly you can't even tell unless the balance is set all the way to the right and there's no other noise. What could be causing this? Truck is an '03 ext. cab.