Hello and good morning, I would like to measure the rest pressures on the connections of low and high pressure line myself at the car air conditioning system (without having to use an air conditioning service unit) in order to get an indication of the level of the system. And that is screwed into the connection with a pressure gauge, as in the picture. To the 1st question: The internal thread of the connections (see graphic) are probably different from manufacturer to manufacturer? or is the thread size uniform? Possibility 2: M mount anometer on a quick coupling and determine the pressure on this way. to question 2: Is the quick coupling short-term lost in the installation and loosening of climate gas? (like the tyre filling) Never worked with a quick coupling before. thank you and love