Turbinesurgeon

Well it seems these Low pressure ports are in different locations. I’m trying to locate the one on my 83. The previous owner had the system converted to 134A by a reputable shop. The paperwork shows new fittings and dryer installed. I wanted to check the pressure because it’s not cooling as well as it should. Anyways I see the high pressure and port that’s correct but on the low side all I found was an R12 fitting on the pax side fender across from the air pump hose. Is there another port? I can’t imagine the shop serviced the system through an R12 fitting but who knows.

Mrmerlin

Your upgrade/conversion service included the shop adding an adapter port to the high side by the drier so the system could be easily recharged with the 134 refrigerant.

Then to add to the confusion you will have no idea if the system was taken apart and flushed and new O rings installed after that.
Or what kind of oil was used Ester or PAG,
R 12 uses mineral oil,
NOTE mix one of these oils and the system will turn to mud, this usually takes out the compressor.

NOTE flushing the system with AC flush will damage the O rings and they all should be replaced after flushing is done.
Otherwise leaks will follow.

At this point you would be smart to take the system apart and flush it out , measure the amount of oil you remove,
refill with the proper oil.
swap in new O rings,
evaluate the compressor and the flex lines that go to it, maybe replace them
Griffiths makes new 928 compressor lines and sells a new Denso compressor for under 1000.00.
add a new drier and expansion valve and you should be set.

NOTE in the picture, the port shown is the low side.

NOTE Its more common for shops to recharge through the hi side as its easier to get plugged in.
but the system must not be running to do this.

WARNING NOTE you must have the engine off to recharge through the hi side.
The hose is connected to the hi side by the drier and liquid refrigerant is fed directly into the system.

NOTE other wise to charge the system,
you connect to the low side then feed gas instead of liquid into the system while the compressor is running.

Kevin in Atlanta

Correct me if I'm wrong, but that is not a 134A port.

19psi

A shop will use a 30lb keg and have various manifold gauge sets. They could easily charge through the original port.
If I were to convert any of my old cars to 134a (which I never would), I wouldn't bother installing the adapters as they're just another common source for leaks.
Now a shop doing it and listing it on a receipt does bring up a red flag. Can you contact that shop?

Turbinesurgeon

Well it seems to be a reputable Porsche shop,I’ll call them Monday to see what their process is to convert to 134a. The parts replaced are Compressor, Dryer, and 134a fittings. Labor is 3 hours. I just want to check pressure and I got rid of my R12 gauges years ago. Guess I’ll have to chase down another set. The AC was always blowing cold until the other day after I moved the temp switch to hot to see if the heat worked. I’ll look for the blend door closing all the way. The car is new to me so I’m just going through everything.

19psi

On the passenger side of the condenser is a site glass. While the A/C is on, shine a flashlight on it and see if there are bubbles flowing through it. If it looks like foam, you're low. Clear or a few individual bubbles is fine. Clear could also mean empty; however, the compressor clutch wouldn't engage at that point.

I'm betting your charge is fine and it's something with the blend door.

Petza914

Maybe that move of the slider to hot opened the heater control valve and it didn't realize when you moved it back. That will definitely effect the cool feeling of even a working ac system as the hot coolant coming through offsets it. See if when you start the car cold, the ac feels like it originally did and gradually loses its effectiveness as the coolant coming through the HCV warms up.