SL air conditioning - PeachParts Mercedes-Benz Forum

desert · #1 06-19-2011, 02:22 PM

Here is a general question concerning older SL air conditioning. Why do the cheapest cars made today have air conditioning far superior to the SL's of the 70s 80s and into the 90s. I have a 85 280SL Euro and I have had the AC system pretty well completly gone over including a new R12 compressor and it still doesent compare output wise to the cheapest Kia sedan avalable today. I know the old stories about the German engeneers not giving much attention to their AC systems because they are seldom used in their colder climate, which could be nonsense but something must explain why the older AC units just don't compare to todays systems. All they have to cool down is a small SL cockpit but mine has lots of problems here in the Arizona heat but if I rent a $10K Kia it will freeze you out. Any ideas?....Thanks Desert

bclem · #2 06-19-2011, 10:19 PM

I've wondered the same thing for years. I've owned a half dozen older MBs of various models and presently own a 79 450SL, an 80 450SL, a 92 300E an 85 190E and a 90 190E and NOT ONE OF THEM has or had an operable AC or cruise control system yet every pos chevy or ford work truck i've ever owned have always had ice cold air and rock solid cruise.

meltedpanda · #3 06-20-2011, 10:59 AM

yes , not your imagination, their AC systems pretty much suc. I really just think it is design, the compressors seem adequate, in fact I upgraded mine in my 84 300SD ,and the system still was poor for cooling. Perhaps its the ductwork, fan speed, dunno

desert · #4 06-20-2011, 04:45 PM

Yes, I think fan speed has a lot to do with it.I posted here a few weeks ago asking if anyone had tried replacing the fan motor with a much higher speed, more powerful unit but it seems like no one has. We will be hitting 107 here in Tucson in a day or two, time to leave the SL at home because it won't touch that kind of heat but that cheap Kia or Hyundai will still bring the interior temp down to cold in nothing flat. Two bad design faults in an SL, the AC system and the sun visors.....Desert

bclem · #5 06-20-2011, 04:58 PM

I believe I'm going to attempt custom fitting a modern system into my 79 SL. I've scratch built a few kit car and hotrod systems before and the only sticky part I see in an SL refit would be maintaining the stock controls but since the 79 model has that crappy ACC2 system I might redesign the whole shooting match. It ain't rocket science.

desert · #6 06-20-2011, 06:08 PM

Good luck with the project, that's way above my paygrade but if during the process if you can figure out what the inherent problem is with the stock system please let me know....Thanks, Desert

junqueyardjim · #7 06-20-2011, 08:17 PM

Are you running your systems on R12 or R134. I had a nice little 230SL (67) in Glendale with that York compressor hung way down low. It was running R12 and it would freeze us out. But if you are running R134 on those old systems, they probably can't do the job. But we thought the AC was doing really good, especially that long hot summer of 1974, when we had a good number of days over 116 degrees.

desert · #8 06-20-2011, 10:23 PM

A Sanden clone using R12. I'm not sure what compressor the car originally had, the AC might have been added when the car was brought into the States as a Grey model. We were the third owner and got the car around 1998 with only 12K on it after it had sat for a while after the death of the second owner. When we moved to Arizona from inland California I decided to sell it and the guy that bought it completly re-did the AC system, sank a couple of thousand in it. Then his wife didn't want it anymore so I bought it back from him ( at a considerable savings) . He had converted the AC to Freeze12 which wasn't cutting it so I had it converted back to R12 using the Sanden clone. The car only has 61K on it and is in mint condition inside and out, zero rust etc. unusual European Burgundy color so that's why I would like the AC to perform a lot better especially in this Arizona climate but maybe I'm expecting too much.....Desert

neds380sl · #9 06-25-2011, 09:21 PM

I'm in Phoenix, just had the a/c leak fixed on my 380SL, and today went for a long drive through the mountains. It didn't exactly freeze me out, but it was very cold (I've got the convertible top on, w/no insulation), and comfortable. And it was around 110 here today. All of these cars have American a/c gear in them. The only issue with mine is that the foot vents don't work when it's on a/c, but the others are fine. Ned

tyl604 · #10 06-25-2011, 09:31 PM

Guys, I have had my 81 300SD for thirty years and the R12 AC has always been really cold. About ten years ago the AC blew up and I put in another myself. Had it charged with R12 and it has been good to go since. A little low on freon now because I see bubbles in the sight glass but it still puts out decently cold air.

So, except for my 6.3, I have always had good AC's in my Mercedes. SD's, 380 SEL, and 300D.

tyl604 · #11 06-25-2011, 09:41 PM

Guys, I have had my 81 300SD for thirty years and the R12 AC has always been really cold. About ten years ago the AC blew up and I put in another myself. Had it charged with R12 and it has been good to go since. A little low on freon now because I see bubbles in the sight glass but it still puts out decently cold air.

So, except for my 6.3, I have always had good AC's in my Mercedes. SD's, 380 SEL, and 300D.

desert · #12 06-26-2011, 02:53 PM

Like I said, I'm not sure if the car originally came with AC or if it was added after it was imported into the States. Can that be determined by the sequence of numbers that are located under the hood on the crossbar? If so, which numbers would indicate the car came with the AC. My guess is it did and the owners manual has AC instructions in it but since the engine is different from a US model 380SL the european AC might not have been as efficient as the US model. Right now it can't keep up with our 105 temps in Tucson but it's better than nothing at all.

neds380sl · #13 06-26-2011, 10:00 PM

Desert- I'm guessing, but if it was imported from Germany on the grey market, it's probably been added, although I don't know how they'd do that so it looks stock. The 4 years that I lived in Germany I noted that few, if any, German spec cars had a/c. Heck, it snowed one day in September! That said, technically I don't know how to tell if it has been added. Is your hardtop on? If not you might consider intalling it, as it adds insulation.
Ned

rowdie · #14 06-27-2011, 12:28 AM

I have an '81 280SL (parts or rebuild haven't decided) It has not been federalized at all. It has what appears to be Factory AC. Different compressor than my '73 450SL but same manual controls.
The Classic Center should be able to provide you with the build sheet and data card.

jammer · #15 06-27-2011, 02:35 PM

In order of significance, Age and Technology. As most of us should well knowl, age affects performance in multiple ways

. In older cars, the internal seals of the little gates that blend cold and hot air and direct it to the appropriate outlet ducts deteriorate or warp making them unable to separate heated air coming from the heater core from chilled air. If you have even a small gap because the gates don’t seat well no amount of conditioned air can overcome blending the hot air coming from a heater core that’s heating already hot ambient air. Many people try to upgrade their compressors or equipment but I think they would get a lot better results by making sure the cold and hot air are adequately separated from each other by upgrading the gates and making sure the ducts are well sealed too.

As for technology, we all know how much technology has advanced the last 50 years. Take a look at your home a/c or refrigerator in reference to how much more they do with less power consumption, quieter and more reliably and sometimes even cheaper in real terms.