I own a 1995 Pathfinder LE and I was having a similar problem with mine. What I did to fix mine was I replaced a few of the easier to get to o-ring s and took a tire valve core remover to tighten the low side valve core.
I did it this way for many reasons but for the purpose of testing and avoiding having to dismantle the a/c system. Try tightening the low side port first to avoid that as a leak point then either add a small bottle of r134a or a leak detection fluid. If you add the r134a and the compressor immediately kicks in like it did in my case then your all set. If it doesn't then I would change all the orings