The primary function of the receiver/drier in your A/C system is to receive and store some liquid refrigerant from the condenser. This liquid refrigerant settles on the bottom of the receiver/drier where a pickup tube with a filter screen on it picks it up and sends it to the inlet of the expansion valve.

The receiver/drier acts as an accumulator in this function, storing extra refrigerant and oil during periods of low cooling demand on the A/C system.

The receiver/drier also contains desiccant, which pulls moisture from the refrigerant in order to keep the A/C system free from contaminants.

If you are working on your A/C system, and must open the system for any reason such as replacing the compressor, condenser or even a refrigerant line, it is highly recommended that the receiver/drier be replaced.