AC leak detection.

This relates to my 1996 s10 specifically, but the methodology should be the same for any car AC system.
My 1996 s10 2.2 auto had a slow leak. I had to top it off once a year to
1.5 years or so. Then it was fine. Now, i topped it off and it sucked down to zero. So now i have a much bigger leak somewhere.
I do have a vacuum pump and gauge set. Last night i pumped it down and it held at 30 when i took the pump off . This AM it was back to zero. Before i pumped it down, i changed the two orings to the condenser. It was a little greasy by them, but it was hard to tell if it was from refrigerant leak or motor.
So, now i still have a leak after changing the condenser orings. What is the best leak detection strategy? I see there is red dye, and UV dye. Any reason to use one over the other? I have a light bulb UV light, but not a proper AC tool UV light. The compressor was a little greasy too, but i have not changed the orings on it yet. I do have a battery sniffer leak detector also, but got it used and am not sure if it works properly or not. I see the auto parts stores have a cheapey looking UV light that runs on two AAA batteries. That looks pretty cheapy to me.
So at this point, what's the best way to proceed? How much of a charge should i put in to detect the leaks before it all leaks out again? What color or kind of dye?
If it is the compressor front seal, how advisable is it to try to change it? The compressor was working fine otherwise. I know you need a clutch puller. Do you need a special tool for the front seal? The speciality tool suppliers list them.
The O-ring connections on the evaporator look clean with no grease on them. Same with the two on the accumulator. Its hard to tell about the ones on the back of the compressor.
Last question, O ring color. I thought the green ones were for R134. It had black ones on it. The auto parts stores had black, green, red and
blue. I put two blues ones on the condenser because that was the only size O'Rileys had that would fit. Whats the difference between the colors? Are there black ones now that are 134 compatible?
Bob
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Bob,
You stuffed a lot of questions in the message. I'll answer one. Sounds like the leak is big enough now that you can find it with a soap solution. Rather than putting dye and more expensive refrigerant in the system, and then you have to let it run and leak out again to see the leak areas. You should pressurize the system with dry nitrogen or carbon dioxide (both non explosive with the oil in the system). Don't run the system when you do this. Everything is turned off. I don't recall what the maximum pressure is for testing on cars, but somewhere it may be stated on a label. May be start at 150 PSI. Go too high and you'll blow yourself up.
Then get a windex spray bottle with a soap solution, pretty thick, and spray it where the leaks might be. You'll need a flash light and maybe a mirror. You should see bubbles, or foam if it's small. What you want is clear liquid soap on the fitting, not foam when you squirt.
A refrigerant leak sniffer is good too. If you have your hoses on the system, just crack a fitting a bit, the sniffer should pick it up. That's much easier
Good luck.
Dave

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On Tue, 17 Aug 2004 13:21:29 -0500, BOB URZ

Chances are it is the shaft seal leaking. The best way I have found to find a leak is to put a can in and then run by an a/c shop with a sniffer and have them pinpoint the leak for you. Most will do it for free or a minimal charge.
I haven't ever changed the shaft seal on one of those compressors so I can't offer any advice on that one.
Steve B.
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