^^^
1) Measure voltage between 1 & 2 pins
2) Install Poti's body to get voltage accordingly to diagram.

Diagram:
x = voltage between 1 & 2 pins
y = voltage between 1 & 3 pins
blue line = min value
green line = max value
red line = optimum value
So, for example, if you get 5,5 V between 1 & 2 set 0,6 V between 1 & 3.

Good luck!

Attached Thumbnails