Guys,, the AC system on modern vehicles are NOT a DIY job,,
The car has to go on a proper AC machine, which in basic terms, vacuum's the system, then hold that vacuum, to check for leaks,, If the vacuum drops, a dye is added with the gas, to help find the leak !!
If OK, a lubricant is then added, followed by the gas, depending on the system, around 700-900 grams of R134, for a full fill !!
You can and do lose gas if on R134, without having a leak, a lot of vehicle manufacturers now work on a check every 2 to 3 years The old R12, which is now illegal, never seams to lose pressure,
Lack of use, does them no good, run in the winter as well, ! even if only for a few minutes,