VDOT A/C System

VDOT A/C SYSTEM

The Variable Displacement Orifice Tube (VDOT) refrigerant system employs the constant run V-5 compressor. The V-5 is a variable displacement compressor that can match the air conditioning demand under all conditions without cycling. The basic compressor mechanism is a variable angle wobble-plate with 5 axially oriented cylinders. The center of control of the compressor displacement is a bellows actuated control valve located in the rear head of the compressor that senses compressor suction pressure. The wobble-plate angle and compressor displacement are controlled by the crankcase-suction pressure differential.

A/C CAPACITY DEMAND-HIGH
When the A/C capacity demand is high, the suction pressure will be above the control point and the valve will maintain a bleed from crankcase to suction; when no crankcase suction pressure differential exists, the compressor will have maximum displacement.

A/C CAPACITY DEMAND-LOW
When the A/C capacity demand is lower and the suction pressure reaches the control point, the valve will bleed discharge gas into the crankcase and close off a passage from the crankcase to the suction plenum. The angle of the wobble-plate is controlled by a force balance on the 5 pistons. A slight elevation of the crankcase-suction pressure differential creates a total force on the pistons resulting in a movement about the wobble-plate pivot pin that reduces the plate angle.

EQUALIZING SYSTEM PRESSURE
When the engine is turned "OFF" with the A/C system operating, the refrigerant in the system will flow from the high pressure side of the orifice tube to the low pressure side until the pressure is equalized. This may be detected as a faint sound of liquid flowing (hissing) for 30 to 60 seconds and is a normal condition.