System Details

The new air-conditioning systems for use with R-134a refrigerant are different from the older R-12 systems in many ways (refer to "Overview of System Changes" illustration):





Refrigerant:
R-134a typically is stored in light blue containers, and the containers have 1/2" - 16 ACME fittings instead of the 7/16" - 20 or 1/4" flare type fittings on R-12 containers. R-134a differ schemically from R-12 in that it does not contain chlorine (chlorine destroys ozone). Refer to chart for physical differences.


Note:
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.

R-12 should NEVER be charged into a system designed for R-134a. R-134a should never be charged into a system designed for R-12. The refrigerants are NOT COMPATIBLE, even in small amounts. Attempts to charge an automotive system with the wrong refrigerant, or mix refrigerants, will destroy the air conditioning system.





Compressor:
The compressor has been redesigned to work with the refrigerant. Melt bolts will not be used anywhere in BMW R-134a systems. A small pressure relief valve (PRV) has been incorporated into the compressor. This allows protection from overpressure, but only allows the minimum amount of refrigerant to be vented to the atmosphere.

In addition, the compressor seal materials have been changed to be compatible with R-134a. The compressor clutch has been modified to cope with the higher torque necessary to compress R-134a at high temperatures.

When servicing or replacing a compressor, always cap off all open fittings when not in use. Do not allow a compressor (even a "failed" unit) to sit open to the atmosphere. The lubricant and refrigerant will absorb moisture, and form an acid that damages new components and prevents analysis of "failed" units.