Hose Material, Condensor, and Receiver Dryer

Hose
Material:
Both the high and low pressure hose materials have been changed to be compatible with R-134a. Instead of the NBR used in R-12 applications, the inner layer of R-134a compatible hoses is comprised of chlorinated isoprene isobutylene rubber (CL-IIR). This material retains R-134a. In addition, the new R-134a hoses allow less moisture to permeate into the system. R-134a compatible hoses will be marked with a white stripe down the length of the hose. Pipes and insulated tubing may also have a green "R-134a" label for clarity. Again, it is important to note that parts may seem physically compatible between systems, but in fact are totally incompatible due to fittings, sealing methods, and/or material differences. Refer to parts information to verify compatibility before replacing parts.

Condensor:
Pressures in an R-134a system can be higher than an R-12 system, especially at high temperatures on the high pressure side of the system. The condenser has been redesigned to cool more efficiently, with thinner tubing and increased fin density. In addition, the condensor does not use copper in its construction. In the right circumstances, R-134a in combination with PAG oil and moisture has been shown to transport (dissolve) copper. As a safety measure, copper has been eliminated from the BMW R-134a systems. An R-12 condensor should not be used in an R-134a system.





Receiver-
Dryer:
The basic design of the receiver-dryer has not changed. However, while R-12 systems typically employ silica-gel as a desiccant (drying agent), R-134a systems utilize zeolite as a desiccant. The drying capacity (per weight) of zeolite is only approximately 25% that of silica-gel. In addition, R134a dissolves desiccants designed for R-12 and may transport them through the system causing blockage and damage. The R-134a compatible receiver-dryer also employs a special ball-spring pressure valve to relieve the system in the event of overpressure. Therefore, only Receiver-Dryers designed for R-134a can be used in an R-134a air conditioning system.