Volvo Repair: a/c, taking chance, freon

Question
1991 740
ac worked last year. Now needs freon. Must I have system purged etc. Or should I just add freon, taking chance.

Answer
Hello Charles,  Well,the first thing to ask is 'do ya feel lucky'! A/C systems hold only about 2.5 lbs of freon,she's a 91 vintage and now could be the opportunity to up-grade.The degree of cold that you are feeling and how fast it cools can indicate how much is left in the system.R-12 is un-availible,there is what is named 'Auto Frost' the generic of R-12,but I would be upgrading.If you were to.. dare I say... sell her,the system needs to work and be current.This should help in your decision. Thank you and good hunting!  PKD