The receiver drier is located after the condenser on the “high pressure” side of the system. It has a filter and desiccant sealed in a container. Its job is to temporarily store refrigerant that has been liquefied by the condenser and to remove dirt and moisture that could cause damage to the refrigeration system.
Sometimes there is a glass window on the top of the receiver drier which allows technicians to check the condition of the refrigerant, but this has been phased out now on most vehicles. It is referred to as a “sight glass.”
The big fact about receiver driers is that they are a serviceable item. They are a filter and should be viewed as such. All the other filters on a vehicle such as the oil filter, air filter and fuel filter are regularly replaced – if not, then the vehicle will not operate correctly. The same is the case with the receiver drier. If it is not replaced, it will become clogged and potentially release the debris around the system, causing blockages and damage. It is cheaper in the long run to replace the receiver drier regularly than flush the blockages out of the system and/or replace major failed components such as the compressor.
Sometimes on small vehicles, the receiver drier is fitted into a tube on the end of the condenser, making it difficult to spot.
A receiver drier is fitted with a thermal expansion valve. If you cannot find either, it means that the system is fitted with an orifice tube and an accumulator.