Why you should change the Accumulator / Drier

by Staff Writer

Don't be confused with the jargon, typically a receiver/drier is used on import vehicles and an accumulator is used on domestic vehicles. They are essentially the same type of part and function in a similar manner according to the a/c system. The drier is used before the evaporator and after the condenser. These units are usually found on the high side of the a/c systems which use a thermal expansion valve. This type of metering valve needs liquid refrigerant.

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Using a receiver/drier or accumulator ensures that the valve gets the proper liquid refrigerant. Functions of a receiver/drier or accumulator include:

1) To receive liquid refrigerant and maintain a certain level of liquid at the bottom at all times in a properly charged system.

2) To trap and absorb moisture using a stack of pellets called desiccant and filter out contaminants or non-condensables.

3) To keep the liquid and gas divided.

The receiver/drier or accumulator are typically an oval-shaped, bottle-like metal unit and some are attached to hoses. A sight glass can be found on the top of most import driers, such as the mercedes units. An a/c technician will use this sight glass to charge the system. If vapor bubbles are visible in the sight glass, the a/c system is not operating under the proper conditions. For a R-134a a/c system, the use of the sight glass is not suggested, as cloudiness and oil which separates from the refrigerant can be mistaken as bubbles. That leads to a dangerous overcharged condition.

The dessicant which removes moisture from within the receiver/drier or accumulator does not come standard. Each receiver/drier or accumulator will vary. The desiccant type can be found on a sticker located on the receiver/drier or accumulator. It is important to check prior to installation because some desiccants are not compatible with R-134a. Most new receiver/driers and accumulators now use a dessicant type XH-7, which is compatible with both the R-12 freon and R-134a freon.

Suggestions for the maintanence of your receiver/drier or accumulator:

1) Change the receiver/drier or accumulator each time an a/c system is empty regardless of the reason for loss of refrigerant.

2) Replace the drier every 3 years, because desiccant pellets will break down and clog up the expansion valve. Thus causing system shut down and perhaps damage to the compressor as well.

3) Think of the receiver/drier or accumulator as a disposable item, same as you would fuel, oil or an air filter.

4) Anytime any part of the a/c system is changed, the receiver/drier or accumulator should be replaced too to prevent corrosion and moisture in the a/c system.

NOTE: that moisture is the most harmful enemy of the air conditioning system. If any moisture is in the system, it will combine with the refrigerant to form hydrochloric acid which is extremely corrosive to metal components.

Again, it is vital that the receiver/drier or accumulator is replaced when servicing an a/c system. If you do not change the receiver/drier or accumulator there will usually be serious damage to the other parts of the system, which could prove to be very costly. Don't jeopardize being back at square one on a later day, always change the receiver/drier regardless. Industry standard also dictates that there be proof of replacement of the receiver/drier or accumulator at the same time of installation of a compressor for the warranty to be valid.

It's the oil in the refrigerant that absorbs moisture and holds debris in the system not the freon r12 or r134a. Replacing the drier / accumulator, in addition to evacuation, will assure better performance.

The receiver-drier must be changed each time a system is empty regardless of the reason for loss of refrigerant. It should also be changed every three years, because the desiccant pellets will break down and clog the expansion valve. This will in turn cause the system to become inoperable and May damage the compressor.

The receiver-drier is strictly a disposable item and is thought of in the same terms as a fuel, oil, or air filter. In fact, if any component fails or is replaced for any reason, the receiver-drier must also be replaced to prevent corrosion and moisture in the system.

The receiver-drier performs three functions:

-It filters the system of non-condensables.

-It receives the liquid refrigerant and maintains a certain level of liquid at the bottom at all times in a properly charged system.

-It contains a stack of pellets called desiccant (drying agent) to trap and absorb moisture. NOTE that moisture is the most harmful enemy of the air conditioning system. If any moisture is in the system, it will combine with the refrigerant to form hydrochloric acid which is extremely corrosive to metal components.

Replacing the receiver-drier is essential when servicing the A/C system. Whenever you replace a component of the A/C system you must also replace the receiver-drier. If you do not change the receiver-drier there could be serious damage to the other parts of the system, which could be very costly. You must also have proof of changing the receiver-drier in order to receive a compressor warranty.