What is the most typical location of slow leak in the AC system?

Most common leaks are rubber hoses (they slowly deteriorate until they're porous) and the radiator/condenser (depending on weather: if it freezes in winter, water gets between the thin metal sheets, freezes, expands and distorts them, eventually a weld will break).

With components of the different automobile manufacturer's being made by different companies, I don't know that there is a way to put a finger on "typical location" of leaks. Even within a given manufacturer, say Toyota, they may have multiple suppliers for the same part.

In all AC systems there are common areas that have potential to leak; seals, hoses, condenser, dryer, connections, etc.

The Toyota Hybrid AC system not needing service is misleading. That would have to be under perfect conditions, which do not exist. No matter how sealed the system, external damage to the system can cause leaks. If debris damages the condenser coil or a hose, the system can be compromised.

On top of that, systems can fail.

I've found leaks in O-rings, crimped on ends have leaked, hose leaking through the side wall about 6" long, condensor, evaporator, compressor seal and O-rings at the pressure switches sometimes will leak and shraeder valves. Pretty much anywhere but the dryer but even their O-rings can leak.

I quit adding a can of freon near the end of last summer to my 07 Kw t800 dump truck so I could stay cool 3 days right? I'm thinking mid September.

I checked the pressure for the 1st time this evening and it had 5PSI in the AC lines. So I got out the Nitrogen bottle and charged the system up to 107 psi static. That's what this truck will have in it when the motor is shut down. It held 2.5 hrs without budging. I know for a fact if I charge it back up in 3 days it will leak down enough to where the compressor won't come on which around 24psi on the low side gauge.

I now have it vacuumed down to 250 Microns and that is very slowly going up and before I unhooked my equipment it was up to 340 after about 2 hrs.

Its a very slow leak and I can't find it to save my life. I've soaped the lines over and over with pressure on the system and nothing under the hood bubbles.

My bet is its the evaporator inside the dash or the compressor seal but doubting the compressor seal a bit I've already dyed the system once.

I'm gonna charge it and add some dye again. Usually pressuring the system - some people use shop air - and soapy water in a spray bottle will find any leak under the hood within minutes.