What type of refrigerant do I use on a 2002 jetta gls

A technician that has the REQUIRED certification to handle refrigerant according to EPA regulations will know the answer. You can look for telltale information under hood.

Agree strongly about refrigerant handling certification being required in accordance with US EPA Section 609. However, R12 was last used in 1993 model vehicles, and not since. Your factory fill refrigerant was R134a.