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Old 07-27-2002, 08:53 PM
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Exclamation Air Conditioning-Please Help!

I have a question about my car's A/C. I have a 1985 380SE Mercedes (Euro spec) The problem that I am having is that my A/C did not blow cool air during the day when it was hot or when I was stopped, but it blew cooler air when the sun is down, it is cool outside, or when I am travelling at higher speeds. Even so, the air that it blew was not that cold. When I brought my car to Midas to be checked, the mechanic told me to convert from the R12 system to the 134A, and I did so. They fully recharged my system with 3.5 to 4lbs. of freon. They also put in a dye to check for leaks. They found none and yet my problem still persisted. I was told that my evaporator could be the cause of my problem. So I had them replace it along with the expansion valve. This was pretty expensive for me. Still there has only been mininal improvement. It blows cool air, but it does not get that cold. The mechanics are now suspecting that it may be my compressor or receiver/dryer. This may be cost me another pretty penny. Could anyone please shed some light on my problem before I have to pay more money to my mechanic. My wallet is starting to feel the pain.

Broke and Sweating in Chicago
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Old 07-27-2002, 10:50 PM
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Join Date: Aug 2001
Location: Houston, Texas
Posts: 393

How did the tech fill the freon without a working compressor ? I dont know about your car but in my 260E and almost every other car, you have a little glass window on or near the drier that tells you if the compressor is working at all. You are likely to see some vapours in that window or bubbles if you are low on freon. Sometimes, the main belt that runs the compressor is not tight enough and so the compressor does not work effectively when engine rpm drops. Ckeck belt tension also. As far as I can tell, it is highly unlikely that you have a intermittent compressor, either it works or it does not. If you see something happening in the window then the next thing to worry about is the condensor fan. Is your condensor fan working ? if it is not working or if it is wired wrong (i.e. if it is blowing air away from the front of the car rather than towards the engine) then when the speed is low the compressed freon will not be cooled enough before it goes to the evaporator and you will not get cold air. You can check the air flow by holding a small piece of your newspaper in the front, the paper has to be sucked towards the condensor otherwise it is not wired correctly. Also check your engine fan, make sure it is working adequately. Is your car running hot ?

If you cant check these things yourself, take it to a reputed MB tech not Midas OR you can take it to a repair facility that sells A/C parts only, i.e. just A/C repair facility. I dont think changing from R12 was necessary and neither was a new evaporator. The only thing that can go wrong with an evaporator is a leak and it looks like you did not have that. Mercedes benzs have very easy checkup methods provided the tech knows about it. I would look up yellow pages and pick a tech that has been in business the longest.


Saumil S. Patel
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Old 07-27-2002, 11:21 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
It never ceases to amaze me how people take a diagnostic problem to a Midas. They obviously don't have a clue, and I wouldn't expect them to.

They would be lucky to understand the refrigeration system let alone a manufacturer specific problem , let alone a grey market manufacturer specific situation.

This kind of work needs exact answers not guesses. If I thought they had a chance of dealing with the car I'd avise telling them they gave you no value and to straighten it out. But, hopefully you will learn a lesson. The only thing cheaper than a true professional is DIY (and thats not true always).

You can find true professionals at dealers and many independents. Any true professional trapped at a franchise auto repair facility deserves my pitty.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 07-27-2002, 11:27 PM
RSH RSH is offline
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Join Date: Jul 2002
Posts: 106
Converting from R12 to 134a was a mistake, 134a has only 75/80% the cooling capacity of a good R12 system, there should be a sticker under your hood that says what the R12 capacity of your air conditioning system is, when useing 134a you normally use 85/90% of whatever the R12 capacity is, the amount you stated in your post sounds like it could be over charged which will cause poor performance, you cannot use the site glass technique with a 134a conversion, you need to monitor the temp as it is being charged and stop at the lowest temp reading.
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Old 07-28-2002, 01:52 AM
Registered User
Join Date: Oct 2000
Location: Taiwan
Posts: 21

Converting a R12 to R134a is definitely a mistake. I don't think the Midas guys can fully understand the AC operation in your MB. As Steve said you need to find a mechanic who really knows MB AC system.

Since you can get cool air when ambient temperature is down. I am suspecting the recirculation flap get failed thus the outside hot air get mixed with the cool air.

I am not familiar with 85 380SE. I'd recommed you take some time to search this site for a clue.

Sorry for not being help.

Charles from Taiwan

94 C220 AMG style
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Old 07-28-2002, 08:56 AM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 11,232
It probably just needed a little more r12 to make it right. I agree, if it was cooling some then converting to 134 was a mistake.
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