A/C System Changes And Version Characteristics
Audi models produced after October 1992 are equipped with a revised air conditioning refrigerant system.
This revised system uses the new R-134a refrigerant. This refrigerant contains no chlorinated fluorocarbons (CFC's), which are suspected of causing damage to the earth's ozone in the stratosphere.
The major system differences are:
- New refrigerant and refrigerant lubricants
- New or changed NC components
- New servicing procedures and servicing equipment
A/C systems using R-12 refrigerant use a mineral oil based lubricant. R-134a systems use a synthetic oil known as PAG oil. The two refrigerants and refrigerant oils must not be mixed or component failure will result.
Vehicle Information Label (Audi 100)
Because of this and other design changes, components from the two systems are not interchangeable. Audi R-134a system components have metric threads to prevent them from being installed on R-12 systems, which have UNF threads. R-134a components can also usually be identified by the term R-134a placed somewhere on the part.
If you are working on an R-134a system and a marking is not visible, make sure to check the part number prior to installation.
The equipment used to service R-134a systems is also different. New recovery machines must be used which also recycle the R-134a refrigerant for recharging. System charge amount is now best determined by measuring the weight of the refrigerant for greater charge accuracy.
Audi R-134a systems use a smaller refrigerant charge than comparable R-12 systems. Because of this, proper refrigerant charge level is very critical.
Because of the R-134a system design, refrigerant system evacuation and charging is now done only through the high pressure side. The service port is also a special quick connect coupling to prevent attaching R-12 equipment. The service port location is:
- Audi 90 Left front condenser
- Audi 100/S4 Right front condenser
- Audi V8 In high pressure line next to right front shock tower