Air Conditioning: Receiver Drier, Drier, Desiccant

What It Does

These components are responsible for capturing water moisture within the charged air conditioning system (the part of the system that controls refrigerant (commonly called “freon”) pressure.). To a limited degree, they can also capture debris within the system.

Why This Matters

Water moisture in this part of the system can freeze to ice and then interfere with proper refrigerant flow (which will increase vent temperature and may even cause loss of cooling in the cabin.) Acid formation resulting from trapped moisture is also a concern to some professionals.

Possible Problems

Ice formation:

Ice formation can form a blockage at the expansion valve. This will inhibit a/c cooling and may even eliminate a/c cooling until the symptom subsides. Since flow through the expansion valve becomes limited or eliminated, the compressor may also starve for lubricant. A small ice element can have a major impact on a/c cooling at the expansion valve because of the small size of the inlet path that it affects. Similar concerns could affect accumulator-type systems with orifice tubes. (These orifice tubes, again, provide a small path refrigerant flow.)

Acid formation and damage:

It is commonly held that water moisture trapped in the a/c system can encourage acid formation. The concern there being (or including) air conditioning system leakage caused by the acid eating away at metal and creating a hole for the refrigerant to leak through. While this is a commonly-held concern, it does not have full consensus for R134 a/c systems. (Regarding the R1234YF systems, that is a subject that deserves research given that the recent introduction of these systems into the automotive marketplace.)

Water Intrusion:

Obviously, water moisture getting into the a/c system is a concern. This is most likely to occur during air conditioning repairs, which often require opening of the system and thus exposing it to the water moisture present in the outside air. However, proper service practice uses a deep evacuation to boil off water moisture in the system prior to charging the system. So how else might water get into the system? One concern is that the low pressure side of the system pulls water moisture in from the outside air if that part of the system drops below atmospheric pressure. This creates a situation where the outside air may actually want to push INTO the system past a weak seal. It has also been claimed that refrigerant rush in the system can pull in water moisture (a similar effect to how blowing air through a small hole in a hose, toward the hose end, can begin a siphon effect.


We do not take a firm stance on whether acid formation is a significant concern in R134 systems. Nor do we take a firm position on whether water intrusion due to temperature differentials or a rush/suction effect is either possible or common enough to matter. There are likely engineers that can help answer such questions, but at this point in time, we don’t have as much reputable information as we’d like to have. Knowledgeable input can go both ways, and these concerns are deserving of further research. But we would point out that automotive manufacturers pay to include the driers when the vehicles are manufactured, and this comes at a cost to the manufacturers (in other words, they’ll need reason to incur that cost.)

All that said, two concepts can help make a decision on whether or not to replace drier elements. One is that a drier that has seen many years of service and then gets exposed to moisture in the ambient air cannot be expected to fully function (if at all.) Second, automotive manufacturers still commonly equip a/c systems with these driers. Since these driers cost them money during the assembly process, they are not installed “just because.” (Especially considering the production scale and how much even a few dollars per vehicle adds up over a production run.) So while we don’t have all the data we’d like, we know that automotive manufacturers have input from their engineers, and they continue to equip systems with these driers, which again, after many years of usage and then exposure again to ambient, moisture-carrying air, cannot be trusted to function any further. It does appear to us that drier replacements can help to prevent more costly failures requiring replacement of components like compressors, evaporators, and condensers, but we’re not going to claim that leaving an old drier alone is highly likely to cause a problem – IF – the a/c system is properly evacuated prior to charging.

Recommended Parts

  • OE grade
  • Denso
  • GPD
  • Others would be pending verification or checks