Had all three sets of O-ring on the compressor replaced and system fully charged in late March. Yesterday, the system stop working again. With black light, I found there are a trace of dye around the low pressure side connectors (black arrows on the picture). However, at the shop in teh day light, we could not see those trace marks I saw last night. And this A/C shop is not a Mercedes specialist and they have no clue what are those two tubes (marked with red arrows). Strangely, we did a large UV spot on the wall (far left red arrow).

Looks like the leak from that connector is so bad that it shoots to the wall. Is it possible? Could I just tighten those two bolts or do I need to replace the o-ring in it? Where to buy O-rings?

Looks like I will have to spend $15 to get a 609 certificate so I could buy R12 on e-Bay. I know which is the low pressure end. Do I just hook a can to that low end or do I need to jump the compressor first?

Very much appreciate your help.

Sorry, my pictures are too big to upload now. I will work them an dupload them later.

here are the pictures. So I was told the line with red markers are the fuel lines but why are they connected to the low pressure line?

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Did you look for dye in the condensation drain water while the system was still cooling? If there is dye in that, then the evaporator would be suspect.

For problem cases, the best way to find the leak is a shop that has nitrogen and a good electronic leak detector. They will put in 2 oz. of R22 and then pressurize the system to 200PSI with nitrogen. The reason for R22 is that it is much better detected by an electronic leak detector.

Hope this helps,

Cools the fuel before it reaches the Fuel Distributor.

The cooler can leak internally

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thanks for everyone's inputs. Here are some general questions.

Is it more common to have the low pressure side leaks or the high side? Isn't the low side has a vacuum rather than positive pressure? How long does one shot of dye last in the system and outside the leak? Do I need to inject dye at every recharge? Would I see the dye leaked out from a year ago? Under which condition does it leak faster, - A/C on or A/C off?

This guy told me that he vacuumed to the max and waited 20 minutes w/o seeing any drop. But my system is empty within 40 days. Last time it was teh low side o ring on the compressor. This time I could see a trace of dye using my powerful research lab black lamp at the low side (per picture above). The small light (battery powered) the shop is using could not see these dye spots.

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__________________
[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."