Receiver Dryer: Description and Operation
A/C Refrigerant System Component Functions, Overview
Receiver drier
The receiver drier acts as a refrigerant reservoir for the system. Any moisture in the system is absorbed in the drier desiccant.
CAUTION!
The R-134a receiver drier is identified with a green label and MUST NOT be used in R-12 Systems (drier desiccant is only compatible with R-134a refrigerant). Likewise, NEVER use an R-12 receiver drier in an R-134a system.