2004 Mercedes-Benz ML500 Air Conditioning Receiver Drier Assembly Replacement Cost

The air conditioner receiver drier assembly is a protective device that removes moisture from the air conditioning system. Of course, there is liquid refrigerant at all times inside the air conditioning system, but water moisture inside the system reacts in a harmful manner, creating a caustic substance that can cause damage to the air conditioning assembly. The air conditioning receiver drier assembly looks like a silver or black jar with one air conditioning line going in and one going out. It may be installed near the firewall in the engine bay, or as a part of the air conditioning condensing unit.

As refrigerant is pumped from the air conditioning compressor, it flows as a high temperature, high pressure liquid through the condensing unit to be cooled. Once cooled, it is still high pressure, but slightly lower temperature, and this liquid will then flow through the air conditioning receiver dryer assembly, or simply 'receiver/drier'.The liquid refrigerant will flow into the receiver/drier, create a pool of refrigerant in the bottom, and pass through a desiccant bag which absorbs non-refrigerant moisture with small absorbent beads. The refrigerant, now free of moisture, moves out of the receiver drier assembly clean of contaminating moisture, and continues down the path towards the evaporator.

The most common symptom of a faulty receiver drier is the appearance of leaks in the air conditioning system. As mentioned before, water in the refrigerant will create a caustic substance that will quickly deteriorate seals in the air conditioning system, which is why the receiver/drier is used. Also, the receiver drier can cause a clog, which will prevent the high pressure side of the system from moving refrigerant to the low pressure side of the system. The result will be low pressure on the high side service port. The pressure in the system is likely to appear equalized due to a clog in the receiver drier.

The only portion of the air conditioner that would require immediate attention is the air conditioning compressor. This is because the air conditioning compressor is driven by a belt that drives other components. Since the receiver drier is only involved with the air conditioning system, it will not affect how the vehicle runs or drives. Those who live in high temperatures should consider the effects on children and seniors, as the air conditioner can be a necessity in some situations.

Every time the air conditioner has lost pressure through leaking or being left open for service, the receiver drier will likely need to be replaced. Since the desiccant bag absorbs moisture at a highly efficient rate, any time in open air will cause the desiccant bag to fill through humidity, and become useless. Otherwise, the air conditioner accumulator drier is most often replaced due to a faulty air conditioner condensing unit since many are attached.

The air conditioner receiver drier assembly is only one point of failure in the air conditioning system, and any servicing technician must diagnose the air conditioner as a whole. Refrigerant pressure must be checked on the high pressure and low pressure side, which will normally provide an understanding of where the problem may be, and where the technician should investigate further. Keep in mind there are electronic components that must be checked with computerized scanning equipment to verify accuracy and functionality, and mechanical components that must function properly as well. Typically the receiver drier would be suspected if leaks are found in multiple places, or if another component must be removed and replaced. Furthermore, if the technician finds that the high pressure side is too low in pressure, and the low pressure side is nearly the same in pressure, the receiver drier will be suspected of a clog.

Evacuating the air conditioning system is necessary when performing any repair which involves opening a refrigerant passage in the air conditioning system. The caveat to that being if the system has lost pressure due to a prolonged or large leak. Once the system is evacuated, the receiver drier will need to be removed by disconnecting all mounting hardware and using specialized disconnect tools to remove the air conditioner lines. Replacing the receiver drier is a matter of refitting the lines, replacing any removed components and recharging the system for testing.

We recommend replacing the receiver drier any time the system has been opened, especially in humid environments. The amount of time needed to perform a repair on an air conditioning system may be short enough to maintain the existing drier, but if the technician feels the desiccant bag in the receiver drier has potentially absorbed too much moisture from the air, it should be replaced. Also, never discharge refrigerant to atmosphere, as this is not only illegal, but can cause chemical burns.

It is important to note that all air conditioners do not use a receiver drier assembly, but instead, some use an accumulator to perform the same function. Some units have the air conditioning receiver drier attached to the air conditioning condenser, and when this is the case they must be replaced as a unit.

Air conditioner repair is seldom achievable at home, and will require expensive evacuation equipment, a manifold and gauge set, creating a vacuum in the system, and charging the system. Aside from the lack of equipment that most DIYers will face, there is a danger of harm to person, equipment, and the vehicle when repairs or diagnostics are performed incorrectly. When it comes to servicing the air conditioner, it is best left to the pros.