we have talked about this valve before, but it is so easy for a student or new tech to get them mixed up, I am covering it again in detail and this time I cut one open.
https://www.achrnews.com/articles/91003-working-with-compressor-service-valves
https://www.hvacknowitall.com/blogs/blog/170187-the-king-rules-only-one-land#.YPis7OhKiM8
source
