Does the ac charge unit fit all types of vehicle low side service port?

They are universal across all types of vehicle for the refrigerant type.. e.g., older vehicles which used R-12 (CFC-12) refrigerant all had the same R-12 schrader valves, and all vehicles with an R-134a (HFC-134) system have the same R-134a schrader valves. This is as they come from the factory... vehicles owners may often change this. For example, an R-12 system converted to R-134a might still retain the R-12 schrader valves.