Refrigeration System Description. Buick Park Avenue 1998

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1998 🢒 Park Avenue 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Refrigeration System Description

Variable Displacement Orifice Tube (VDOT)

VDOT Refrigeration System


(1)	A/C Pressure Sensor
(2)	Muffler
(3)	High-Side (Discharge) Line
(4)	High-Side Service Port
(5)	Condenser
(6)	Liquid Line
(7)	Expansion (Orifice) Tube
(8)	Evaporator
(9)	Low Pressure Liquid
(10)	Low Pressure Vapor
(11)	High Pressure Liquid
(12)	High Pressure Vapor
(13)	Accumulator
(14)	Desiccant
(15)	Oil Bleed Hole
(16)	Low-Side Service Port
(17)	Low-Side (Suction) Line
(18)	High Pressure Cut Out Switch
(19)	High Pressure Relief Valve
(20)	Compressor

The variable displacement orifice tube (VDOT) system is comprised of the following components:

•	A variable displacement compressor

•	A fixed expansion tube (7)

This system matches the air conditioning demands under all modes without cycling. The basic compressor mechanism is a variable angle wobble-plate with 5 cylinders. The 5 cylinders are oriented around a common axis. The center of control of the compressor displacement is the control valve. The control valve is actuated by a bellows. The control valve is located in the rear head of the compressor (16) that senses compressor suction pressure. The crankcase-suction pressure differential controls the following conditions:

•	The wobble-plate angle

•	The compressor displacement

When the A/C capacity demand is high, the suction pressure will be above the control point. The valve performs the following functions:

•	Maintains a bleed discharge gas into the crankcase

•	Closes 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. The force on the pistons produces a movement about the wobble-plate pivot pin that reduces the plate angle.