Refrigeration System

The Variable Displacement Orifice Tube (VDOT) refrigeration system is comprised of a variable displacement compressor and a fixed expansion (orifice) tube. This system can match the air conditioning demands under most conditions without cycling. When the A/C capacity demand is high, the suction pressure will be above the control point, a control valve will reduce the amount of the internal bypass of the refrigerant.

Depending on engine usage, the compressor is cut off. Following are some examples of conditions resulting in compressor cutoff:
^ Wide open throttle
^ Low idle speed
^ Low air temperature
^ High P/S loads

When the engine is turned to OFF with the A/C system running, the refrigerant in the system will flow from the high pressure side of the evaporator tube orifice to the low pressure side until the pressure is equalized. This may be detected as a faint hissing sound for 30-60 seconds and is a normal condition.