servo turns all the way left and does not center

[Espeefan]

Sounds like the potentiometer is not being driven by the output shaft of the servo anymore. If the potentiometer is not centered, the servo is going to move the direction it thinks it needs to, to satisfy what the potentiometer feedback is telling the servo.

If you can turn the servo shaft, with the power off, both directions, to it's hard stop, and everytime you turn the power on and it moves the same direction, then I would disassemble the servo and check to see if the gears and pot are all right. Might be an easy fix.