I found on port to my AC on back of compressor is this the high or low side valve cap on Schroeder vavke is green. System is presently r-12 but does not cool down efficiently, although compressor was replaced back in 09 it looks brand new car used very little. Someone suggested duracool? has anyone had any luck with that stuff? Also I need to find high side shader vavke for gauge hok up. Any help would be appreciated thanks!