Depends, the 'low pressure' side is the side generally serviceable with a can of R134A you can buy at your local auto parts store. This side generally runs between 35-55 PSI, give or take, depending on ambient air temperature, elevation, etc. The high pressure side is generally not serviceable by the average consumer. if you're faced with a leaking line, take it to a pro who has the equipment to capture any refrigerant that needs to be released from the system. mother earth thanks you.
There is a STICKER under the hood that tells you how many LBS. it will hold.
6
1.5 lb of Freon or about 2 an 1/2 12 oz cans.
18 gallons
1.75 lbs. of refrigerant
3.7lbs
18 to 18.5 us gallons
7.5 quarts of oil
A 1990 Cadillac Deville air conditioner should hold 46 oz. R12 Freon. This should be verified through the owners vehicle manual.
7 to 7.5 quarts for the 4.0 V-8
most likely 14 to 16 gallons
around 31