Components Overview

Refrigerant Circuit with Restrictor and Accumulator:

NOTE: Arrows indicate direction of refrigerant flow.

1 - Compressor
2 - Condenser
3 - Restrictor
4 - Evaporator
5 - Accumulator





- The compressor is driven by a belt on the engine when the A/C clutch engages (A/C on).
- Low pressure refrigerant from the evaporator is compressed by the compressor. After compression, the refrigerant (now high pressure) flows to the condenser.

NOTE: The compressor contains refrigerant oil (PAG oil) that can be mixed, at all temperatures, with R-134a refrigerant. A label on the compressor indicates that compressor is for R-134a systems only.

Condenser:

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

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

Evaporator:

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

- 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 then is suctioned by the compressor.





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

- 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 taken in 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: Image shows the Evaporator/Restrictor from an Audi 90 model. Insert restrictor into evaporator in direction of arrow -A-.

- The restrictor restricts and controls refrigerant flow to the evaporator, thus lowering the 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 upstream of the restrictor filters out any dirt or particles. Another strainer downstream of the restrictor atomizes the refrigerant before it enters the evaporator





- O-rings seal the connections between A/C system components
- Use only new red or green O-rings that are compatible with R-134a refrigerant and refrigerant (PAG) oil
- Always use correct size 0-rings (dimensions -a- and -b-)
- Do not reuse O-rings, always replace.
- Lubricate O-rings with refrigerant (PAG) oil before installing.





- The pressure relief valve is mounted on the compressor. At approx. 38 bar (551 psi), the valve opens to vent excessive pressure. When system pressure is reduced to approx. 30-35 bar (435-508 psi), the valve closes to prevent total refrigerant loss.

A/C Refrigerant System 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 a green mark (stripe) or the lettering "R-134a"
- Hoses and lines are secured with threaded connections. Always properly torque hose and line connections.

High Pressure Service Valve:

NOTE: Image shows the condenser and service valve of an Audi 100 model.

A - Service valve connection (soldered to front of condenser)
B - Schrader valve insert
C - O-ring
D - Cap with seal

- Use only the specified R-134a quick coupling connectors when servicing the refrigerant system.
- Before removing the valve insert from the service valve, discharge A/C refrigerant system.
- Always reinstall cap -D- over service valve
- Only a high pressure service valve is used for A/C system servicing. A low pressure service valve is not installed in the A/C system. Carry out all A/C system service operations (i.e. discharging, evacuating, and charging) through the high pressure service valve only.