I have a, 87 300 SDL, and the AC compressor doesn't dissengage. The clutch works as when I take out the klima, it stops, but the compressor doesn't stip with it in while the car is running, even with the heat on full blast (not def). Does any one know what would cause this?? And where I coudl start to fix it??

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All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic

Your clima relay could be stuck. You can carefully remove the cover on the relay and check it. The only other thing could be something in the A/C controls that is energizing the clima relay.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

I took apart the klima relay (an old one), and checked it. There was a copper part that was blown apart on the circuit board. There are no moving parts on it. I soldered that copper part together, and it worked. They problem is that I'm still left with the same problem as I had before. The AC compressor doesn't disengage. Might the CCU be at fault??

__________________
All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic

Pull the Klima.

Turn the key to the #2 position.

Check for voltage on socket #5 by using the socket and a battery ground.

If you have voltage on socket #5, check for voltage again on socket #5 while using socket #10 as the ground.

You should have voltage on #5 (with socket #10 as the ground) when the three left buttons are selected on the CCU. When you select economy, the voltage should disappear.

If the voltage remains with the economy switch selected, the CCU is toast.

Maybe I don't understand how the Mercedes climate control works. I don't have an owner's manual. If I have any of the left 3 buttons pressed, the AC compressor should be running. But if economy and off are selected, the AC compressor shoudl be off?? Do I have this right??

__________________
All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic

It appears you now understand how it works. Even if you set the dial fully for heat, the compressor will come on if any of the left three buttons are selected. The compressor will not come on if the "EC" or "0" buttons are selected.

-TurboWells