The receiver drier, or dryer, in this Porsche 911 appeared to be the original: 22 years old. With factory air cars, the drier is located in the LH side front fender wheel well, located toward the back trailing side of the tire and attached to the back splash panel. Considering that the drier to the a/c system is what an oil filter is to your engine, it was definitely time to replace it.
The drier provides 3 functions to the a/c system
- Inside the drier is a desiccant that removes moisture from the system. As little as a few drops of water in an a/c system will create problems and the desiccant can only soak up so much water:
- Internal moisture will freeze up the expansion valve and cause intermittent cooling,
- When water mixes with some refrigerants a very corrosive acid forms that will etch holes through the evaporator, condenser and compressor reed plates.
- The drying agent or desiccant in the old drier was not compatible with R134a refrigerants. If you are converting to R134a it is not worth the gamble to find out otherwise, so when converting to R134a you need a different type of desiccant compatible with R134a refrigerant and oils. Kuehl driers use XH9 type desiccant which is compatible with both R12 and R134a refrigerants.
- The drier serves as a reservoir for the system, providing liquid refrigerant to the expansion valve when called for.
- Most drier elements act like a filter which retains system contaminants which could clog the expansion valve or damage the compressor.
- With R12 refrigerants most driers have a sight glass to assist in monitoring the level of refrigerant. The 911 typically used a “floating ball” in a side mounted site glass. With R12 you would typically be near optimum refrigerant level when the ball is just floating at the top. During our particular project we are not concerned with the sight glass when charging with R134a, we are more interested in the weighed amount of refrigerant (measures in ounces) and system pressures (low side and high side, measured in psi).