VDOT A/C System

The Variable Displacement Orifice Tube (VDOT) refrigeration system has a V5 compressor. The V5 compressor can match the automotive air conditioning demand under any conditions without cycling.
The basic compressor mechanism is a variable angle wobble-plate with five axially oriented cylinders.
A bellows actuated control valve controls the compressor displacement. This control valve is located in the rear head of the compressor that senses the suction pressure of the compressor.
The crankcase suction pressure differential controls the following features:
^ The wobble-plate angle
^ The compressor displacement

The following actions occur when the A/C capacity demand is high:
^ The suction pressure is above the control point.
^ The valve maintains a bleed from the crankcase to the suction.
^ No crankcase-suction pressure differential exists.
^ The compressor has maximum displacement.

The following actions occur when the A/C capacity demand is lower and the suction pressure reaches the control point:
^ The valve bleeds discharge gas into the crankcase.
^ The valve closes off a passage from the crankcase to the suction plenum.

A force balance on the five pistons controls the angle of the wobble plate. A slight increase of the crankcase-suction pressure differential changes the total force on the pistons. This change affects the movement around the wobble-plate pivot pin and reduces the angle of the wobble plate.
The compressor has a unique lubrication system. The crankcase-suction bleed is routed through the rotating wobble-plate. This routing permits lubrication of the wobble-plate bearing. The rotation acts as an oil separator. Some of the oil is removed from the crankcase-suction bleed and rerouted to the crankcase. The rerouted oil can lubricate the compressor mechanism.
Depending upon engine usage, the compressor is cut off when the following conditions exist:
^ Wide-open throttle
^ Low idle speed
^ Low air temperature
^ High power steering loads

The refrigerant in the system flows from the high pressure side to the low pressure side of the expansion (orifice) tube when the following conditions exist:
^ The engine is turned off.
^ The A/C system is operating.

The refrigerant continues to flow until the pressure is equalized. This action may cause a faint sound of liquid flowing (hissing) for 30 to 60 seconds. The sound is a normal condition.