[Bob B.]

I think there's a little confusion here. These systems have 2 valves in them. First is the POA (Pilot Operated Absolute pressure) valve, which controls the pressure in the evaporator. It is a silver valve in the line from the evaporator to the compressor, and has 4 connections on it (in, out, a small oil bleed line, and small equalizer line to the expansion valve. The other valve is the expansion valve. It controls Freon flow into the evaporator. The expansion valve is mounted on the inlet to the evaporator. It is shaped like an inverted 'L', and is usually a cad-plated gold in color. The large line goes to the reciever/drier, it has the small equalizer line to the POA, and a small line that terminates in a sensor bulb under the insulation tape on the outlet line from the evaporator. Expansion valves are available from many suppliers, and usually run around $65 or so. Original type POA valves are no longer manufactured. New ones are out there if you look for them, but expect to pay $300. There is a 'POA Update' kit available. It eliminates the POA valve, and controls evaporator pressure by cycling the compressor off and on, like a modern system. It works, and it's a lot cheaper than buying an original POA valve. The problem is that the compressor clutch on these old system was not designed to cycle on and off like a modern system, and will wear out faster than it normally would. It doesn't seem to cause and abnormal wear to the A6 compressors, though. Since the compressor clutch is also available, and not terribly expensive, a lot of people with older G.M. A/C systems go this route.