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* * AUTOMOTIVE AIR CONDITIONER The Receiver/Filter/Drier provides three functions: (1) It is a tank that holds excess refrigerant and the refrigerant that leaves it usually goes up a pickup tube and past a sight glass. Under normal operating conditions, vapor bubbles should not be visible in the sight glass. (2) It has a filter in it to remove small amounts of debris from the system. * AUTOMOTIVE AIR CONDITIONER (3) It has a chemical in it that treats the refrigerant by removing moisture and acid. There are different types of receiver-driers and different desiccant materials used in them. Some of these desiccants are not compatible with R-134a and receiver-driers will be marked for use with either R-12 or R-134a. Newer type receiver-driers use a special desiccant that is compatible with both refrigerants. * AUTOMOTIVE AIR CONDITIONER R-134a requires a different desiccant (XH7) in the accumulator or receiver/drier because the molecules are smaller than R-12 and quickly fill up the holes that absorb moisture in XH5 desiccant. This can lead to acid formation and sludging as well as desiccant breakdown in some applications. It is a good idea to replace the receiver-drier each time the system is opened for repair or anytime moisture and/or debris is of concern. * AUTOMOTIVE AIR CONDITIONER 5. Accumulator Orifice type systems use an accumulator that is connected directly to the evaporator outlet and stores excess liquid refrigerant. Since liquid refrigerant going into a compressor can do serious damage to the compressor, the main purpose of the accumulator is to isolate the compressor from any damaging liquid refrigerant. * AUTOMOTIVE AIR CONDITIONER Accumulators, like receiver-driers, also remove debris and moisture from a system. It is also a good idea to replace the accumulator each time the system is opened for repair or anytime moisture and/or debris is of concern. * NOTES TO THE TEXT 1. Your air conditioning system is made up of a compressor, a condenser, an evapo