Good evening Gentlemen!

Condition: The AC system used to be charged with R134a, then was recently converted back to good ole, more efficient R12.

Symptoms:
On '84 300 CD, the AC compressor shuts off even when the temp inside the car is not yet cold. The AC would cycle on and off even when the ambient temp is above 90 deg, car is at idle, and both windows are rolled all the way down, with the fan at the hi/fast position, the the temp wheel/tab is on the min/blue position. The AC now cycles cold-not cold-cold not cold. The AC don't do it when it was still R134a until it was converted back to R12. But it never got cold when it was R134a, except when it is raining or driven at night.

Questions:
1) Could the Evap temp sensor be the culprit?
2) Is there any way to adjust or tweak this to cut OFF late, probably at least before freezing point, around 34 to 36 deg F? Right now, it seems like it is cutting off somewhere around 42-45 deg F. If there is a way to adjust, can somebody please teach me how to do it?
3) Is the Evap temp sensor NFG, or MB was just too conservative to adjust this to cut OFF at a higher temp, so a new ETS will fix the problem?

But before I start changing and buying new part, I just wanted to try if adjusting it will do the trick. "I don't work at the dealer, which means I am not a parts changer and I'm trying to be a real mechanic"
I may have no idea what I am doing but if it's broke, then it has to be fixed, and the worst thing that can happen is for me to tear it up some more. Remember, "If it ain't broke, don't fix it"?

Any help, ideas, suggestions, and knowledge will be greatly appreciated! Thanks in advance!

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'85 300D Turbo - CA Version