Cadillac Repair: a/c 1990 deville doesnt work, 134a freon, r 12 freon

Question
I recently cleared all the codes on my 1990 cadillac deville. After clearing all the codes I tried turning my a/c onbut it didn't work. I ran a code check once again and I received the code F48 its the only code on there and its never been there before. I have a sheet that says that F48 means very low a/c refrigerant pressure condition. What does that mean and what do I need to change. Also when I look under the hood a round metal thing(which I think is the compressor) says r12+r134a flow. Does that mean my car is r-134a compatible? Thanx in advance

Answer
I have never seen this type of TAG. I would imagine since the car came originally with R-12 freon, That someone converted it to the R-134a freon.

CLEAR the code from the computer and add additional freon using a set oif AC gages. You may have to jumper the AC relay in order to get the compressor running to install the freon.