Automotive Air Conditioning Receiver
The receiver-drier is found on systems that use a thermal expansion valve. This type of metering valve requires liquid refrigerant. Therefore, to ensure that the expansion valve gets plenty of liquid refrigerant, a receiver is used. It is a storage device for liquid refrigerantThe primary function of the receiver-drier is to separate gas and store liquid refrigerant. The secondary purpose is to trap water vapor and filter out dirt.
The receiver-drier may have a sight glass built in. This sight glass is often used to charge the system when using refrigerant R12. Under normal operating conditions, vapor bubbles or oil streaks seen in the sight glass would usually indicate a low charge. Be Careful though, it could also indicate an extreme overcharge as well.
The use of the sight glass to charge the system is not recommended with refrigerant R-134a, as cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles. This type of mistake can lead to an overcharge or dangerous high pressure condition.
There are variations of receiver-driers and several different moisture trapping Desiccant materials are in use. Some of the moisture removing desiccants found within older driers are not compatible with R-134a.
It's possible to install some receiver-driers incorrectly. Pay close attention to the markings that designate inlet and outlet.
