Automotive Air Conditioning Information Forum

Yo,
got question
I am not sure of one thing, does the oil combine with the R134a in the AC system? I observe that the use of AC with a leaking system when gas is low( not too low to low press sensor will work) leads to compressor failure. I suspect that a small amount of R134 dissipates the oil poorly, and the compressor does not have the lubrication of a tight and full AC system. it can be like that ?

The oil is carried with the refrigerant. For practical purposes think of it as a fog of oil moving along with the refrigerant (this is not quite right but you will get the idea).
If there is a 134 leak, oil will go with it, and you will lose oil also. You can only lose so much oil before you are in trouble.
If the 134 level is low enough (the low side pressure is low) you will also starve the compressor of the oil that is still there, because it won't be returning to the comp very well

Sounds like you'd best fix your leak.......

The oil is diluted and loses much of it's lubricating properties depending on how much gas is mixed in. If only a little it won't matter as it'll soon vapourise.

How the oil exists depends on where it us in the system.
In a liquid line it is in a sort of solution, a leak of liquid R134a is leaking also oil.
In the discharge line it's an incredibly high velocity high turbulence mixture of liquid oil an vapor R134a, a leak of R134a also leaks oil.
In the suction line it is a sream of oil along the bottom at low capacity conditions like with variable compressor or at idle. At higher capacity conditions, it's like an annular flow stream around the entire ID of the pipe or hose. Possible to leak R134a with no oil escaping at low capacity conditions, at high capacity oil should leak out with R134a.

When the system is off. R134a can easily leak out without taking any oil with it.