If it has what subford is talking about, it will have a very small tube coming out of the valve, that curls over and disappears behind some insulation. Like he said, it will have a bulb under the insulation, and when the fluid expands and contracts in the bulb, it will move in the small tube and open the valve.

They must control the refrigerant in the front by turning the compressor on and off, and control the rear with this valve. I know enough about refrigeration just to be dangerous.