I have read as much as I can here on the board about the AC. I am thinking the problem is the CCU, but I hope not. They seem to be hard to find without paying through the nose for one. Here are my symtoms:
CCU set to AC and wheel down as low as will go :
On vehicle initial start of the day...AC works great anywhere from 5 to 20 min. Then stops cooling, starts blowing abient air. Stop and start the vehicle ,AC works again anywhere from 2 to 5 min.....,or not at all. Sometimes as I drive down the road with my wonderful ambient 90 degree air blowing in my face, the compressor kicks on and I have AC..nice and cold. I have sat and watched the compressor kick on for 5 sec and then off for 5 sec and on and off etc. etc. until the car warms up and then it stays off. Sometimes, when in one of the extended cooling cycle(5-20 min) as I turn a corner the compressor kicks off and I'm back to the wonderful abient air temp again!! Does anyone have any Ideas? I hate to just throw a CCU in there and that not fix the problem. Ideas and test procedures are greatly appreciated. I really hate taking it to a shop, I enjoy the challenge and am pretty handy with a wrench. Plus I enjoy learning. Thanks in advance for all your help.

Jeff

Your symptoms sound like a ACC controller. What I found on mine, and many here report the same thing, are cracked solder joints. The circuit boards inside the controller are arranged in an "H" pattern and the corner solder joints crack from vibration, etc. Not too difficult to pull, open it up and repair with a soldering iron.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Thanks for the reply... I guess I'll be pulling the CCU and looking at the solder joints. Do you have to add more solder or can you just touch the cracks with the iron so the cracks repair themselves ?
thanks

Jeff

Usually, you can get away with just touching the iron to the existing solder. However, touch-up is not the best method because the solder components tend to separate with repeated heating. New solder is best.

Since newer solder is a different "blend", I chose to remove the older solder with braided-copper wick and re-attach with new soldering, resulting in nice, shiny, long-lasting joints. It is your choice really.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Now that I have the cover off the CCU and looking at the circuit board...Where would the cracked solder joints be and how do you pull this board to look at the other side ? I have included a pic . How do you identify the joints that need to be resoldered? Can you you see the cracks? It is pretty obvious I am new to this, just trying to learn .
thanks abunch
Jeff

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The problem could be the CCU........or it could be the Klima or it could be one of the signals to the Klima.

You could throw parts at it.........or you can troubleshoot it properly with this procedure:

http://www.peachparts.com/shopforum/showpost.php?p=1546012&postcount=70

before you do anything.. check the fuse in the engine.. its not a regular fuse its a strip fuse. i had the same issue with my 87 300DT bought 2 climate controlls and stuff.. then read before replacing it that there was a fuse i looked and the fuse was bad. its a strip fuse contained in a rectangular plastic container. look arround for that i hope this helps

Well I had my hopes up for the fuse......removed it and replaced with a jumper and no luck ,same symptoms. Thanks for your reply. Now I know there is a fuse in that spot.

Jeff

Where was that strip fuse located ?

where are u located?
larry perkins lou ky

the strip fuse should be loated on the right side of the engine nearing the seperation from the engine to the fuse box. mine is close to my ABS box. if needed ask and ill post a picture of where mine is located

86Benzor, try the troubleshooting guide that Brian Carlton provided and if it turns out to be the pushbutton unit, the discolored area on that circuit board would be highly suspect. You will probably need to remove the board to see what is on the other side and if it is repairable. Hopefully so, as the version for that model is pretty pricey.

Thanks Brian for chiming in, as I didn't realize that the controller had changed for the '86-87 models.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Hey thanks for all the advice. I'm starting the trouble shooting guide that Brian sent today if time will allow. If the problem does turn out to be the unit, how do you rermove the board to access the top side? I can't figure it out. Do you remove the push buttons? If so, how? I do not want to force anything to a point of no return....
thanks Jeff

Removing the boards on the later ('86 onward) units is quite a challenge. I wouldn't recommend such a task. I wouldn't bother with it myself. Too much effort with no guarantee of success.