I have low cooling from my A/c (300CE R12). normally it is low in R12.
When I get the R12 filled, the first few days it is really cool.
Then it starts to get less cooler. My mechanic filled it with air at high pressure and left the car & the A/c running for two hours. no drop in pressure.
He believes the R12 leaks very slowly from the compressor & it would be better to replace the compressor.I would like to know the options.
The temperatures here are 47C now in the summer.
I have noticed that cooling is much beter in the toyota's & the Nissan's here in Dubai.
Will a compressor from these cars fit & will it give a better performance.
Too many questions as it keeps getting hotter.

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300CE 1989 Euro Model.
ML350 2011.

You have a leak, question is, from where is the leak originating? Replacing the compressor as a stab in the dark to fix a leak is an expensive solution. My mechanic has a hand-held sniffer that can tell you where the leak is - absolutely without guessing. You need a mechanic who has the same sniffer. Then you can solve the problem once.

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- Brian


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

Don't you already have the same compressor as Toyotas and Nissans?

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2012 E350
2006 Callaway SC560

Can your explain your statement;

My mechanic filled it with air at high pressure and left the car & the A/c running for two hours. no drop in pressure.

Sounds like he removed the freon and filled the system with high pressure air. If in fact he did that the oil circulation for the compressor was surely affected in a negative way.

Am I properly interpreting what you said?

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Yeah dpetryk, you interpreted it correctly.

When he leaves it running for a couple of hours after filling it with air at high pressure, there is no drop in pressure. After that he again fills it with R12 & only after the car has been running for a couple of days there is low freon.
Also after researching for a few days I understand that the best bet to increase cooling is to increase the airflow over the condensor i:e to have a better fan, correct me if I am wrong. what is the best fan available that will fit right in.
I know lots of questions, but I am really sweating.

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300CE 1989 Euro Model.
ML350 2011.

Does your car have one electric fan out front, or two?

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2012 E350
2006 Callaway SC560

It has only one electric fan

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300CE 1989 Euro Model.
ML350 2011.

That procedure of filling the system with air seems bogus and very detrimental to the system. First off, you cannot find the leak using air. Air will not register on a leak detector. Real shops use a mixture of nitrogen with 5% R12 freon so the detector has something to pick up. They pressurize the system up to about 300 psi and then go sniffing to find the leak. Second, putting air into the system will carry moisture in with it. You don't want any moisture in the system. Third, running the system with air in it is not the same as freon because the air will change phases like freon does. And as a result the high and low pressures will not be like freon. It will not carry the lubricating like freon etc. Thats not doing your compressor any good at all. Also a very small leak will be hard to detect any loss of pressure over a short period of time.

I have had to chase several leaks in my cars and they have all been O ring related in the hoses. Usually in the high side connections at the compressor or hoses on the high side.

Sounds like you need to take your car to a shop that knows what they are doing.

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Starting in about 1990 the US cars came with two fans.

Perhaps that could be retro-fitted to your car.

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2012 E350
2006 Callaway SC560

I agree with the comments that the mechanic you have now is creating more problems than solving them. A mechanic who fills a/c system with air does not know what he/she is doing. Change the mechanic right away. If the leak was through the compressor, a proper mechanic should be able to tell you immediately, there are refrigerant leak detectors that can easily find this. The leak that is real difficult to find is in the evaporator behind the dashboard, but this too is generally inferred based on not finding a leak anywhere under the hood. Also if you keep filling R12, at some point you also have to fill some oil, with each leakage episode, you are also loosing some compressor oil. Use a heavier oil, i.e. use StopLeak or something like this to fill some oil along with freon.

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Saumil S. Patel

That's for sure. Sometimes a sniffer will not even detect a leak in the evaporator. And if it's not leaking much in the way of oil you can not see the dye coming from the evaporator box drain holes either.

An update to my cooling woes.
I took it to another a/c shop.
They replaced the evaporator.The previous evaporator was only 3 yrs old.
anyway I had cool air for almost a week after that the engine temp went upto 120 C in traffic. Found the fan not working, the fuse was blown, replaced the fuse and that blew too the next day.Took it to an electrical garage. They found the fan was shorted .Replaced the fan & the resistor.The a/c again gradually got warmer and finally after two weeks it was blowing only air. With outside temp in the range of 40 to 47 C it was really bad.
Took it back to the shop which had replaced the evaporator.
They checked there was no R12. it had completely leaked out.
They pumped in air again & checked with applying soap water on the hoses searching for bubbles(This method seems to be the normal method in these places as I have found most of the A/c shops/indies use this method here).They found some tiny bubbles on the hose at the low pressure side.
They replaced the two hoses & assured me that now everything would be OK.
But it was not really cool enough. I thought the low cooling was due to the high temperatures outside & the mechanics tell me these old mercedes do not cool good.
After a week again on the way back from office the a/c suddenly started blowing hot. Found the compressor & the fan was not running.
what is the problem??? Have to take it to another shop.
Do not know whether to keep it or sell it off.

Very long post, but had to cry somewhere.

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300CE 1989 Euro Model.
ML350 2011.

R12 pressure is there. it has not leaked out.

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300CE 1989 Euro Model.
ML350 2011.

Three years! Ouch! Do you think it was really leaking?

Bull. Both of mine get uncomfortably cold here in hot, humid Alabama.

I wouldn't give up yet. You probably have a simple problem here compared to what you're already suffered through.

Has the AC worked at all since it suddenly quit? Has the compressor run again since then?

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2012 E350
2006 Callaway SC560

STOP HAVING AIR PUMPED INTO THE SYSTEM. Pumping air into the system ruins the drier. Did you know that it is recommended to replace the drier each time the system is opened? That's because the drier gets exposed to the atmosphere and the dessicant quickly becomes saturated with moisture. Pumping air into the system is much much worse than just briefly opening it up to atmospheric humidity.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280