Air conditioning accumulators, filter driers, and receiver driers
The air conditioning receiver drier, sometimes referred to as the filter drier, functions just as its name would indicate: as the filter for the refrigerant system. These “filters” are cylindrical in shape and always have an inlet and an outlet. Receiver driers are always used on A/C systems which also have an expansion valve. When locating your receiver drier, you’ll find that they look similar to a metal tube or can, and will always be found on the high side of the refrigerant system, usually between the expansion valve inlet and the condenser outlet. Many later-model vehicles have the receiver drier built into or on the condenser assembly. Most of the time, when directly attached, the desiccant bag is replaceable by itself.
Many vehicles have what is also referred to as an air conditioning accumulator. Although the function of an A/C accumulator is very similar to that of a receiver drier, it is typically much larger and is on the low-pressure side of the refrigerant system.
Accumulators and driers always have a desiccant bag inside. The desiccant bag, normally activated by moisture (oil and refrigerant), absorbs H2O (water) and traps debris. Once activated, it will trap any water in the system. When an A/C system is opened, the natural humidity in the air enters the A/C system, and the desiccant bag can immediately become completely saturated and be rendered ineffective. If the desiccant bag cannot absorb any additional moisture that remains in the system, a chemical reaction between water and refrigerant can create an acid that will eventually eat though seals and o-rings throughout the air conditioning system. For this reason, it is important that the accumulator or receiver drier be replaced any time the A/C system is opened to the atmosphere.
One of our favorite analogies we use to help consumers understand why it is important to change out the receiver drier and/or accumulator is the engine oil example. When visiting your local repair shop to get an oil change, you always replace the oil filter to complement the new oil added to your engine. The same holds true for the automotive refrigerant system. When performing any job where the Freon is evacuated and the system is opened up, it is imperative to replace the drier/accumulator along with any faulty parts. Doing so also ensures you preserve your warranty.