My AC compressor does not kick in. Here is what I know, The fan is on high speed the temperature thumbwheel is set to max blue, there is R12 in the system, there is 60psi on the low side, the auxillary fan starts shortly after you jumper the compressor on, the compressor will start if you jumper it at the Kilma relay terminals 5-7 , The compressor speed sensor 144 produces at least .3V at terminals 9-11 as specd in the trouble shooting flowchart The microswitch 134/1 works , there is continuity between the terminals until the cam roller is engaged. The Klima relay tests good when I swap it into my wife's car, it is the same part #. As far as I can determine the compressor is not being told to start , so what else would inhibit it and exactly where on the car would those items be. My wiring diagrams off the PDF manual are very hard to read. I have a feeling that there are a couple of switches somewhere that are causing the compressor not to start. Anyone have any guidance. Thanks Dan

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91 300D 603.960 (from japan) 194K
92 Toyota Diesel Landcruiser HDJ81-t 116K
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87 300D
97 BMW 525 TDS Wagon 5spd
bunch of Onan and other diesel generators

Could be the pushbutton unit.

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1987 W201 190D

Not sure if these have em but on an 83SD there was an evaporator temp switch underneath the dash next to the expansion valve. This things purpose is to open if freezing temperatures to ensure you don't accidentally turn on the compressor with frozen liquid in there. Just pull the two wires off and jumper them together to bypass for trouble shooting. The switch should be closed always in summer temps.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius