Hi
I need to detect a leak in my cars empty A/C system. It's a 1992 300TE and has never been converted to R134a. I got new R12 but do not want to charge into a leaking system. I read about the method of using 5% R22 and then pressurize with nitrogen.
It looks to me that for a DIYer it may not be economic to purchase the necessary equipment to add the pressurized nitrogen. So I wonder, why not using just R22 alone, without the nitrogen?
Would this make sense, technically and legally?
Many thanks, Bruno

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1992 300TE 160 kmiles

The Nitrogen gives lots of extra pressure to help find the leak. It would be legal to fill with R22 AS LONG AS YOU RECOVERED ALL OF IT AFTERWARDS.

Do NOT run the system with R22 only. It will not circulate the lubricant properly and all bets are off as to what would happen with pressures.

The idea of the R22 and nitrogen is totally for static testing with an electronic leak detector. By making the pressure with nitrogen, you have high pressure throughout the entire system to force the R22 through even a small leak to be detected.

I have my doubts as to how effective straight R22 would be due to lack of pressure.

Good luck,

Thank you very much for your clear explanations, Larry. I understand that it does not make sense to use R22 alone.
Bruno

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1992 300TE 160 kmiles

How do most A/C shops find leaks (besides using UV dye in the charge) I suspect that the evaporator on my E320 is leaking very slightly, but I do not have the correct tools or know how to check this. When the weather warms up here in WI to the point where I need the A/C again I'd like to know how to thoroughly check the system for leaks.

EDIT: Sorry to hi-jack your thread, I will start my own.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE

Actually R-22 circulates mineral oil quite well; that's the combination used in the central a/c of your home. You don't want to use R-22 in an operating mobile a/c because it's the wrong refrigerant. The pressures are much higher. If you're lucky the high pressure switch will just shut the system down. But you may blow out a hose, or the condensor, or damage the compressor.

The idea behind using R-22 with nitrogen is that a combination of 5%R-22/95%N2 is not a "refrigerant", and therefore can be vented without violating EPA rules. That's probably bending the rules a bit. As well, in the murky haze that is my memory I recall that R-22 is very easy to detect with an electronic leak finder. Hence perhaps 5% is enough.

Personally I like the dye method. Charge up the system, ignore it 'til it don't work again, go look under the hood. My '93 124 had a slow a/c leak - about a pound every year and a half. I used the above technique. It was easy to spot the leak. The system was spotless, except for the expansion valve - it pretty much glowed in the dark. Replaced TXV and all is now well with the world.

My $.02,

- JimY

There is a product called Freeze12 that works very well as a substitute for R12. Cost is about $11 a can. I've used it in a 12 system on a Lexus, and it works very well.

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- Brian


1989 500SEL Euro
1966 250SE Cabriolet
1958 BMW Isetta 600

Diesel Giant has the Freeze12