I hardly come across mini splits. Been doing this for 15 years. Wondering how to check the charge it is a 410A system with 3 circuits. There are 2 larger schrader valves on each circuit. I assume one is the high and low side. Do I have to turn them all down and check each circuit or just one. Any ideas or a link on what to do would be great! It is a 12RLS model specifically a AOU12RLS.