System Review

System
Review:
The new air-conditioning systems for use with R-134a refrigerant are different from the older R-12 systems in many ways. Detailed component comparisons between R-12 and R-134a parts are provided in TRI 64 01 92 (2121). The following is a quick review of important service considerations:

Refrigerant:
Although R-12 and R-134a are similiar in some ways, the refrigerants must NEVER be mixed or combined in any way under any circumstances. The resulting chemical combination can create extremely high system pressures, destroy desiccant, corrode components, seize the compressor, and allow refrigerant to escape into the atmosphere.

Compressor:
The compressor has been redesigned to work with the refrigerant. R-134a and R-12 compressors are not interchangeable in any way.

Compressor
Oil:
The compressor oil used in the R-134a system is drastically different than the mineral oil based lubricant used in R-12 systems. Use of R-12 system oil in R-134a systems will cause the compressor to seize and fall. In addition, R-134a system PAG oil should not be used in an R-12 system. Never re-use old compressor oil.

Seal
Material:
Since the seals are still the same size, always verify the use of correct seals when performing service. R-12 type seals used in R-134a systems will allow refrigerant to escape. BMW has made seals available that are compatible with BOTH R-12 and R-134a. These seals are typically very dark green in color. Refer to current Parts Microfiche.

Service
Fittings:
In order to prevent accidental charging with R-12, the R-134a systems use unique quick-disconnect service fittings on the vehicle. The high side and low side fittings are different sizes (pressure side larger) to assure proper hookup. Any difficulty in connecting service equipment may be an indication of refrigerant/equipment incompatibility with the vehicle's system. Always carefully ascertain the type of refrigerant used in the vehicle's system before performing service. Labels in the engine compartment, typically on the top of the fan shroud, will detail which refrigerant is used in the air conditioning system. Service the vehicle with compatible recycling equipment ONLY. Attempts to adapt and use incompatible service tools will destroy both the vehicle's air conditioning system and the service tool.


Service
Tools:
Never use any R-12 service tools, such as manifold gauge sets, on R-134a systems. Tools retain small amounts of refrigerant and lubricant. Attempting to use the same equipment on both R-12 and R-134a vehicles will contaminate the air conditioning systems.

Refer to Service Information in 04 06 92 (3522) for further information on the essential R-134a charging and recycling station.