1977 saab 99 retrofit

[braxeqot]

Help me pros! I have this old car with a retrofit installed ac and limited experience with ac. I'll try to be brief.

Its just bare essentials and can't get it to cycle off I've had to use parts from 85 saab as there are none available. Maybe I am missing some vital parts here.

After changing the expansion valve it did get cold but never cycled off on max cool. The newer expansion valve has a 1/4" compression nut on a wire in addition to the evaporator tailpipe probe which is all the original had on it.
New accumulator but it is from a bigger vehicle.
It has a schrader valve with a similar male fitting so I thought maybe that was supposed to input high side pressure to meter the valve. Also the old accumulator had wires on it not sure if those were vital to the system basic function or maybe they were to ensure the cooling fan runs when the compressor is on or take pressure readings.
I've also tried three aftermarket thermostat switches.

Flushed it and charged with r134 passages SEEMED clear. When I get the low side up to charge I purge the high side from that schrader and have gotten some fluid there but on my latest try it's about 100 ambient and mostly just air. So I charge and purge air and repeat and never really got cold on the hottest days though it is holding pressure over extended time periods.

I've thought about road testing it since the cooling fan covers only about two thirds of the radiator which is jammed between the condenser and fan. And I should probably find a way to get a high side reading. But I don't really know what behavior is appropriate as far as the pressures at different operating conditions and I'm afraid to push it over the recommended to get it cold but maybe that's what I need to do.

Ideas?

As far as questions how much refrigerant it takes to get charged on an empty system and do you have any way I can tell overcharged from undercharged. Is there such a thing as too much freon when isn't freon supposed to be the only thing in it?

[tbirdtbird]

"I purge the high side from that schrader and have gotten some fluid there but on my latest try it's about 100 ambient and mostly just air. "
This sentence indicates you are not vacuuming the system.

I think you need a pro shop near you.

[JohnHere]

I agree with the previous comment. You should bring the car in to a professional A/C shop...preferably one with vintage Saab experience...to sort-out this setup and to get the system operating again.