This car has the cursed AC servo, which was bad when I got it. I installed a replacement (which I got for $10.00 ) and the blower, heat etc.. works fine. There was no belt on the compressor. I put one on and it would not engage. I checked and had no power to the AC clutch. If I hotwire the compressor it kicks in and cools. Backtracing, I found there is no power getting to the switch on the console. This is as far back as I have been able to trace. Does anyone know what is going on here??

Also there are 2 vacuum lines coming out of the bottom of the AC servo, one yellow and one black. Anyone know where they go or what they do???

Thanks for any help anyone can give me. It's getting hot here.
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Usually the reason there is no power to the AC clutch is a lack of Freon. Although you say it cooled when you hot wired the clutch. There still might not be enough Freon for the system to function properly.There is a switch in the low pressure line and when pressure is to low it breaks the connection between the wires that plug onto it. I would find this switch, it goes on the low pressure line usually by the accumulator. It looks like a sensor with two wires connected to it. Unplug the wires and hook a jumper between them if the compressor runs than It is either low on Freon or the switch is bad.
Also I am assuming you have checked the fuse if not do that first.
I hope this helps.

I had it checked today and it's full. thanks.

Hi there,
The two vacuum lines coming from the bottom of the servo are from a temperature sensitive switch that keeps the blower from running until the engine heats enough to provide warm air. If my memory serves, it allows the blower to run starting at around 135 degrees or so.
Does your AC compressor run when you push the defrost button? If you have a vacuum leak that prevents the AC compressor vacuum control switch #20 from closing, the compressor should still run when you push the defrost button in. The button bypasses the vacuum switch. If you have a vacuum leak, that vacuum switch not turning on the compressor is the first sign of the leak. (The dash AC switch must also be turned on in all positions except the defrost position.)
I suggest you go to: http://unwiredtools.com/vacuum and download their simplified vacuum diagrams. They are correct, but easier to read than the ones in the factory manual. If you have a color printer, print them in color as they show the line colors, also the valve positions for each operation. (Unwired tools makes a digital controller which replaces that nasty servo unit with a solid state unit that works much better.) At any rate, it is fairly easy to track down a vacuum leak using their diagrams. Usually its one or more of the vacuum "pods", the units that operate the flaps in the air paths, that is leaking. The leak in turn lowers the AC system's vacuum level to the point that the AC vacuum switch won't make, causing the compressor not to run. If the leak becomes bigger, the blower vacuum switch won't make and the blower will stop working. The reason those two vacuum switches are there is to turn the compressor and blower off when the heater control "off" button is pressed. (The buttons only operate vacuum lines, no electrical switches behind the buttons.)

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

I tried it out and the compressor does kick on with the defroster. the defrost vent and outside dash vents blow hot and the center dash vents blow cold. Also, I have noticed the vloor vents never blow, so I'm assuming that may be a good place to start looking for a leak. thanks for the help.

Wasn't exactly a vacuum leak. I got the diagram and started checking things out. some of the lines were connected to the wrong t. I switched them back and it works cool as a cucumber. Thanks for the help.