The a/c in my 240d worked on the way home from work yesterday but then I got in it at night to drive and there is good air coming out of the vents but it is not cool. I checked the compressor fuse and all is ok. The clutch is going on the compressor fine but the auxillary fan is not coming on. Today, when I took it for a drive, the a/c worked again. After going to the store and getting back in, no cold air again. Do you think the aux fan motor is shot or could it be in the wiring? I live in Houston and we have another good two months of hot weather or so....

bringing it back up to the top hoping for some replies Thanks

Well, got in it this morning t check and the a/c was blowing cold again. I guess the auxillary fan has nothing to do with it but I thought it should come on when you turn a/c on.

The aux fan is activated by a temp switch on the receiver/dryer. If the refrigerant level is low, the temp at the r/d will not reach a high enough level to close the switch and actuate the fan. You can confirm the proper operation of the fan circuit by jumping the the temp switch on the r/d. (Not to be confused with the pressure switch, which allows the compressor clutch to engage.)
A/C temp switch:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1KG0NMHLI1LP0OXXI1&year=1982&make=MB&model=240-D-002&category=R&part=A%2FC+Temp.+Switch

Thanks for the reply! I jumped it and the fan came on so I suppose the refrigerant is low. If it is low, I suppose I have a leak somewhere. There is an oily area green in color and I see very small bubbles coming from the hose in the area of the attachment. I have attached a picture so you can see what I am reffering to. It is out of focus to the intended area but I am sure you can get the idea. If I do indeed need to replace the hose, should I go ahead and convert to 134? THANKS for your help..

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My advice is: Don't even think about it!!!

I would get it leak tested to determine what is needed to fix it. Could be as simple as tightening a fitting. I converted my 82 300D to 134 several years ago. It can't handle ambient temps above about 85 degrees F. Performance in stop and go traffic is poor. I am going to switch back to R-12.