several weeks ago, I gave up working on my WRX's a/c  (wouldn't hold a vacuum - but I admit I may not have closed-off the center line on the manifold) and took it to a pro. He couldn't find a leak, charged it. I asked about dye and he put some in, worked for many weeks, now, it is blowing hot again.

So, hoping i could spot a bad hose or leaking connection, I checked around tonight with a UV light. No 'smoking gun' really. there are small spots under and around the compressor. The low pressure port cap is bright, but I figure the tech put it back on with dye on his hands. No big blotch on a hose or near comp. or firewall connections,, didn't see anything on brief look around the condenser....

How common would a compressor failure be and could it dribble-out spots around itself?

is the clutch engaging and spinning with the pulley?

Has anyone changed all the o-rings in the system? Compressor is not usually a leak point. Mostly we see discharge hose crimp failures, and o-ring failures. I would buy a new discharge hose (high failure rate), and swap all the o-rings especially at the compressor fittings. Also don't disregard the shrader cores in the fittings. 

GD

A lot of guys never think about checking the tightness of the Schrader valve cores on the low and high ports. It could be that. Even with the caps on, my Ranger leaked through the high port.

Best to replace them.

On our 97 Legacy, it held a vacuum, but the Freon leaked out past the shaft seal on the compressor.

I have seen the high pressure rubber hose get oily from leakage. I think I may have caused it. When I pull the engine, I remove the compressor and lay it in the battery box.

My 08 Impreza had a leaking condenser and evaporator core.  The condenser should be evident with a UV light.  Ideas above are a good start before you get in too deep.

The O-rings that get the most heat are on the compressor discharge line, receiver dryer and condenser.

The evaporator core is not readily visible. You should get in there somehow and look for dye leaks.

 

I did change the o-rings at the comp. Have looked-over the hoses at the crimps. Again, I had a perhaps anomalous vacuum leak, but my 'pro' didn't find anything severe so, he charged it, used dye at my suggestion.

Maybe tonight or this weekend I can be more throrough looking for dye.

comp may still be pulling in but, it won't be long before pressures are too low for that. It stopped cooling.

$$$ is a little tight right now so, if I can find the leak, I'll repair it myself. If not, going back to the pro I guess....

 

Since it cooled for "many weeks" the leak is small and you may not see the dye.

Remove the caps on the low and high charging ports. Cover the hole with your thumb for about a minute. Then remove your thumb slowly and listen and feel for a pisst. That is how I found the leak on my Ranger. I could have used a rubber hose and a low pressure gauge, but my thumb worked.

You also have the option to dump in a can of A/C Pro that contains stop leak. I don't care much for stop leaks, but I used it on our 96 Voyager when I could not find the leak. After 4 years I checked it for pressures and only added a few ounces of Freon.

Don't put stop leak in the A/C system, or any other system for that matter.  Not only are they bad for the system, they generally don't work very well.  Find the root cause and fix that.

It was charged on July 23rd.

I'm unlikely to use a stop leak, too soon for that.

is a leak that takes 5-6 weeks too slow for the 'sniffers' a/c techs use sometimes?

1 hour ago, 1 Lucky Texan said:

is a leak that takes 5-6 weeks too slow for the 'sniffers' a/c techs use sometimes? 

I'm not sure. I don't know if they have something newer than what we used years ago ( the one with a flame).

It's a little hard under the hood with all that air moving.