The pressure when the system is not running doesn't tell you much. It is more a rule of thumb for a quick check.

I am dealing with something similar right now on my TSX. I can easily turn the compressor clutch plate by hand, so I am assuming that the compressor is shot.

 

Ouch....in TX that could be a bad thing in the summer.

Again, I know nothing about ac - I hate electrical but could help with that side of it .....I was only trying to see if there was any change in the system pressures when the engine is off vs when on and ac on. My guess at a way to see if it was an internal issue with the compressor or the expansion valve......I shall bow out of this one

 

OK...

I used a small screwdriver on the high side tap and vented a bunch of that crap, dropping the pressure. Now the compressor doesn't turn-on (expected).

So what is the best way to test the system and decide on a course of action for the least money? Each can of that stuff is like $20!

How about a can of that stuff, and somehow watch for leaks? But then I have to get some special glasses and a flashlight, and that's another $15 or so.