This is a great forum! I am so impressed with all the great answers. I love the other forums, too, but this one seems to be filled with experts who know exactly what they're talking about. I do wish I had come here first.

The system was not in use at all for what was probably years and years. There was a seized compressor on there and no belt. I would imagine it had originally had R12 in it. He put on a brand new compressor and expansion valve, as well as a new evap/drier.

I can't find my receipt...I have to locate it to find the details of the repair so I can share them with you. It sounds like at some point I want to get some R12, don't I? Would R12 not give me as much engine braking if i turn it off and then on again? would it be a lot colder?

Also, I have an old compressor someone gave me off a w123. I can turn it, i.e. it's not seized, but there is a lot of dirt and particles near the connector. I brought it with me to the repair guy for this car and he looked at it and thought it would never last. I wonder if it is salvageable or usable on my 81 300D.

Can you easily turn the "inner" pulley of the a/c compressor that is installed?

There is no way to just answer some AC questions with facts... some amount of philosophy enters the picture... Risk has to be weighed both for cost and in some instances... health... There are places in the US where if you get caught out without help with no AC it can be life threatening... and that problem increases as one ages... or your passengers age... So my suggestions take that into account... along with the idea that having to do something twice or more times instead of Correct the first time.. is a waste of time AND money...
At some point you will probably want some R12.. but that is getting ahead of lots of other things.. first finding out what is in your system at this time being critical.
If you were in Mass... sure... play with that old compressor if you wanted to... but in Ariz or Tx .. NO WAY NO HOW !!!! You need a new compressor if you can find one.. certainly rebuilt otherwise... You will see as you go along.. that the amount of CARE and learning and Labor involved BEFORE you put the AC compressor on... means that you do not want to risk having to do the cleaning process ALL OVER AGAIN due to that questionable compressor being put on and contaminating your system ( AGAIN )....

I'm going to get my front end aligned, then help out a friend I met here in town with the same car I have -- we're going to get his vacuum lines right. I got mine right but his still are not. Then, I'm going to stop by the shop that fixed my A/C, and I'll try to get a receipt. Then I'll report back. :)

Sounds good.. thanks for that info..

I'd go back to the shop and have them fix it. They should warranty their work. Sounds like you might have a bum compressor...

AGREED!

I'm of a mind to edit/delete any posts here and in the future that attempt trolling/off topic messing with arguable info on this forum!

I have some further information. This post might get a little bit long, just a warning :)

This afternoon, before driving the car (cold engine), I tried turning the compressor and it turned smoothly. Then I drove the car in 94 degree heat, and it worked, and seemed to put light resistance on the engine. I stopped for 10 minutes at a shop, and then started it again with the compressor engaged, no trouble. Then I drove home, and it heated up to about 190 or so. When I got home, I let it idle for 5 minutes or so, and the temp increased to 210 or so. All of this time the compressor was left on.

Now, to answer some earlier questions:

First, here's all the info on my invoice. It doesn't specify how much refrigerant was put in, unfortunately:

===

REPLACE A/C COMPRESSOR - REPLACE
DRIER - REPLACE EXPANSION VALVE
-CONVERT TO R134A FREON - FLUSH
SYSTEM AND LINES OF DEBREE. CLEAN
ALL LINES - REPLACE ORINGS WITH
UPDATED O-RINGS-EVACUATE &
RECHARGE SYSTEM -
NOTE -HAVE NO AUX FAN OPERATION
-NEEDS FAN ASSEMBLY & SWITCH ON
DRIER TO OPERATE FAN.

Freon Qty 2 $29.00
retrofit kit 55 9807 901 qty 1 $19.38
compressor 000 230 47 11 qty 1 $299
a/c expansion valve 115 835 00 72 qty 1 $49
A/C receiver drier 116 830 04 83 Qty 1 $42.00
Belt 004 997 93 92 Qty 1 $9.25

===

I know I could have gotten all the parts cheaper...i should have prepared better. He had told me he'd give me dealer pricing on the parts, since my father used to run a small dealer in town, but it seems that he charged me retail. Also, 4 hours labor were charged.

Next, here are some photos I took today:

Temperature after a 20 minute drive using A/C; ambient temp: 93F
http://farm6.static.flickr.com/5293/...2e243c442c.jpg

Temperature after idling for 5 minutes after 20 minute drive
http://farm6.static.flickr.com/5224/...c55fcd35e3.jpg

Top view of new compressor
http://farm6.static.flickr.com/5146/...7cf94158a2.jpg

Bottom of compressor
http://farm6.static.flickr.com/5103/...36e2422b80.jpg

Another view of bottom
http://farm6.static.flickr.com/5095/...278aa6f8d9.jpg

Closeup of bottom with label from CompressorWorks
http://farm6.static.flickr.com/5023/...69877a4489.jpg

Evaporator-Drier
http://farm6.static.flickr.com/5229/...8861da1275.jpg

Very sorry to see that he changed you to R134a..
it is by its molecular nature about 20 percent less efficient than R12 which came in these cars...
How many ounces did he install... that is at the crux of some of the theories ...
as already pointed out.. only Point Eight Tenths of the capacity listed for R12 would be installed when dealing with the R134a... and overcharging is a possibility given your symptoms...
These AC systems were not really designed for South USA...
You do not have an evaporator-dryer... you have a receiver-dryer and then inside the car an evaporator...

You keep referring to the compressor being on... if this is true...and you need to look at the inside part of the front of the compressor to tell if it is actually engaged... then it sounds like the mechanisms meant to CYCLE it are not working correctly... and /or it is overfilled with either refrigerant and/or oil....

Did you fix this

that was noted on the ticket?

Jim, if you are going to play... you are going to have to read the thread....LOL

post 5 says :
"They told me I needed a new auxiliary fan and temp switch, but I repaired the fan easily, tested the switch and circuit according to the service manual
And it works now. It comes on while the car is idling and it is hot out, but only after idling about 2 minutes when outside temp is 95or so. "

leathermang, I don't think this car has a mechanism for cycling the compressor. The switch seems to directly turn it on and off. I can tell from in the car when it's on, since the idle is lower slightly, and there is much less power, not to mention the cold air coming out of the vents.

engatwork, yes, that was noted on the ticket, and they told me about it afterward. However, I removed the fan, took it apart, cleaned the brushes, and reassembled it, and it worked well. Then, I tested the temp. switch on top of the receiver-drier (thanks leathermang) in hot water with a coffee thermometer, as instructed in the MB manual, and it tested out ok. Today, I noticed that when I got home, the fan was running.

Well, I supposed that is possible... some cars run the compressor all the time.. but we need a picture of your console.. the things you push to control your AC and air, etc... and a general pic of the top of your engine compartment...
I am trying to figure out if you have type 2 or 3 AC system.. or something else which I will not be able to help with....LOL
The other possibility has been mentioned... that it is supposed to cycle...but something is not working correctly.... which would give that impression....
You are probably going to need to get a set of gauges and put them on for us to tell more given what you have said....

In much cooler weather the compressor will cycle as needed, but in this hot weather it will most likely stay on constantly.

Do you think you could post a video of you cycling the AC compressor on and off so that we can get an idea of the load that the compressor is putting on the engine...

From what i can tell just by reading your posts, i think your compressor might be a faulty unit.

Leathermang, a 1980 300SD has the servo system, horizontal pushbuttons w/ compressor on/off switch. Which would be ACCII.

In post #8 I linked to a page with this photo of my console:

http://mercedesautoclub.com/sites/de...89-400x300.jpg

It's the older pushbutton system...unfortunately. I have an 81 300D with the newer horizontal layout, and that seems to be much simpler (i.e. no servo).