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 is definitely time to replace it. The drier provides 3 functions to the a/c system:
1) 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:
(a) Internal moisture will freeze up the expansion valve and cause intermittent cooling,
(b) When water mixes with some refrigerants a very corrosive acid forms that will etch holes through the evaporator, condenser and compressor reed plates.
(c) 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.
2) The drier serves as a reservoir for the system, providing liquid refrigerant to the expansion valve when called for.
3) Most drier elements act like a filter which retains system contaminants which could clog the expansion valve or damage the compressor.
4) 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).
1) 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:
(a) Internal moisture will freeze up the expansion valve and cause intermittent cooling,
(b) When water mixes with some refrigerants a very corrosive acid forms that will etch holes through the evaporator, condenser and compressor reed plates.
(c) 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.
2) The drier serves as a reservoir for the system, providing liquid refrigerant to the expansion valve when called for.
3) Most drier elements act like a filter which retains system contaminants which could clog the expansion valve or damage the compressor.
4) 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).
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- The compressor is still driven by the engine, so it is mounted firmly to the case and connected to the Crankshaft by a belt.
- The Evaporator is inside the passenger compartment so that air can be picked up by the fan and sent across the cooling coils and back out through the vents.
- The condenser that is normally placed in front of the radiator in a 'real' car must be placed in the air stream or where there will be a steady high volume of cold air since this is where the freon sheds the heat that it has picked up inside the Evaporator.
- The Receiver/Drier like those most 'real' cars use would be under the hood and have a 'sight' glass on the top so that the technician can see if the system needs additional freon is mounted somewhere on the body in the liquid line that runs from the Condenser to the Evaporator.
- The biggest difference between a Porsche and the rest of the cars on the road is the amount of rubber hose that is needed to connect all these pieces together. In the past this was the biggest problem because all this hose had been made to purposely 'bleed' freon much like your skin bleeds air. The hose was actually pricked through the outer layer each inch or so to prevent the hose from blossoming from the pressure inside. What this meant was that Porsches were subject to the lose of much more Freon than the other cars and thus had to be topped up more often. That's the only downside.
So you see, there is nothing so Mysterious about the air conditioner in your Porsche !
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| This is right rear calipers and rotor. The rubber line directly above the rotor is the oil return line. On the right end of this line is the oil reservoir. |
| This is right drilled, front brake rotor with the calipers removed. The spring and shock are exposed. Just behind the rotor is the wheel speed sensor. On the right, out of the picture are the oil lines, temperature sensor, cooler and oil blower. |
| This are the calipers and brake pads and shims from the front brakes. The wire coming out of the top of each caliper is the ABS sensor wire. The rubber tubing makes sure that all pads on a caliper work at the same time. |
| This is right side of the luggage compartment with the carpeting removed. You can see the gas tank in the center, back. The deflated spare tire is in the fore ground with the tire compressor in the center of it. Next to it is the car battery. On the passenger side of the gas tank is the main fuse and relay panel. On the driver side of the switch box is the fuel expansion tank. The white plastic object in the middle of the right side is the brake fluid reservoir. Just behind the reservoir and behind the blue line is the left side crash sensor. The right side crash sensor is just behind the bronze fuel tank strap on the other side. |
| This is left side of the luggage compartment with the carpeting removed. Just to the right and below to the expansion tank is the hose from the gas cap. To the left of the spare tire, just in view are the ABS control unit and bleeder. Diagonally across the tire from ABD control unit is the ABS hydraulics (under the cover). |
| This is left drilled, front brake rotor with the calipers removed. Inside the left fender is the windshield washer pumps and tank. This side also contains the air conditioner condenser in front of the wheel and receiver/dryer unit behind the wheel. |
| This is left rear brake rotor with the calipers. You can make out the ridge the pads have worn into the rotor. |
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