Components Overview

A/C compressor







The compressor is driven via a belt on the engine when the A/C clutch engages (A/C ON).

Low pressure refrigerant gas from the evaporator is compressed by the compressor. After compression, the refrigerant gas (now high pressure) flows to the condenser.

The variable displacement A/C compressor varies piston stroke and output depending on load requirements and suction pressure.


NOTES:
- The compressor contains PAG type refrigerant oil that is mixable under all temperatures with refrigerant R-134a.
- A label on the compressor indicates that compressor is for R-134a systems only.


A/C condenser







The condenser transfers heat from the compressed refrigerant gas to the outside air which causes the refrigerant to change state from a gas to a liquid.


NOTE: Illustration shows the condenser from an Audi 100 model.


Evaporator







Liquid refrigerant entering the evaporator absorbs heat from air passing through the evaporator fins and cools the air. As the refrigerant absorbs heat it turns to vapor and is suctioned by the compressor.


NOTE: Illustration shows the evaporator from an Audi 90 model.


Accumulator







The accumulator traps the mixture of refrigerant vapor and gas coming from the evaporator. While in the accumulator, the refrigerant vapor turns to gas and, along with the refrigerant oil, is then suctioned by the compressor.

An oil extraction passage is incorporated into the accumulator to ensure that refrigerant oil flowing with the refrigerant does not remain in the accumulator.

Any moisture in the system is absorbed by the desiccant in the accumulator.

NOTE:
- Do not remove caps -A- and -B- until ready to install new accumulator.
- If caps are removed too soon, the desiccant becomes saturated with moisture after a very short time. If this occurs, the accumulator must be replaced.


Restrictor







The restrictor restricts and controls refrigerant flow to the evaporator thus lowering refrigerant temperature and pressure.

Upstream of the restrictor, the refrigerant is hot and under high pressure. Downstream of the restrictor, the refrigerant is cold and under low pressure.

A strainer located upstream of the restrictor filters out any dirt or particles. Another strainer located downstream of the restrictor atomizes the refrigerant before it enters the evaporator.


NOTES:
- Insert restrictor so that arrow -A- points to evaporator
- Illustration shows the evaporator from an Audi 90 model.


O-rings







O-rings seal the connections between components of the A/C system.

Use only O-rings which are compatible with R-134a refrigerant and refrigerant (PAG) oil. Refer to the most recent parts information when obtaining new O-rings. O-rings are recognized by colors (currently red, green or violet).


NOTES:
- Handle O-rings only in a clean working environment.
- Do not reuse O-rings, always replace.
- Always use correct size O-rings (dimensions -a- and -b-).
- Lubricate O-rings with refrigerant (PAG) oil before installing.
- Always make sure to properly install O-rings on line/component mounting flanges/grooves.
- O-ring and torque specifications also apply to threaded connections in the A/C lines.

Hoses and lines
The mixture of refrigerant oil (PAG oil) and refrigerant R-134a attacks some metals and alloys (for example, copper) and breaks down certain hose material. Use only hoses and lines which are identified with the lettering "R-134a".

Hoses and lines are secured with threaded connections. Always properly torque hose and line connections.