Mike,
Behind the t-stat bracket there should be a very small adjustment screw. Turning it either "clockwise", or "counterclockwise" will change the cut in or cut out temperature inside the machine which will determine when you compressor cycling off and on.
It's best to have a thermometer to make this adjustment. There are also contact t-stat's were the probe touched the cabinet, and a non contact t-stats so you want to make sure you know which one you have installed on the machine.
This is only a starting point, but start there...
A nickels worth of free advice,
Testing Thermometer
http://www.fun-tronicsllc.com/index.php?crn=292&rn=1349&action=show_detailOld Thread:
http://soda-machines.com/discussions/index.php?topic=13743.0 Jared