you have *some* volume, but when you turn the knob, the volume won't adjust?
pull the control plate off, and make sure the wires aren't jumping (creating a short) and bypassing the volume. You see, a potentiometer is nothing more than a variable resistor, and if the signal is bypassing the resistor, then no matter what you do, (i.e. turn the knob) nothing changes. Also, if the wires appear to be in order, you could have a bad pot. It's a $4 part.