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AC and cooling fans won't work

(1994 Cadillac DeVille)
in Indianapolis, IN on April 30, 2009
The AC will not come and the cooling fans will not operate. I've replaced the high and low cut out switch, temperture sending unit, checked all fuses and wiring, what am I missing
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Popular Answer
on May 01, 2009
I am assuming that the cooling fans are operating correctly when the engine temperature warrants there operation. The cooling fans will not run with the A/C until the A/C pressure builds to the point where they are necessary, with the compressor not operating the fans are not necessary. There are several things that need to happen for the A/C compressor to turn on. As I recall, the a/c control head sends out a compressor request signal through the various switches which returns to the a/c programmer. If everything is ok to that point the programmer will send an a/c request signal to the powertrain control module and if the pcm says ok a signal is sent to the a/c compressor relay which sends power to the compressor clutch and with a proper ground circuit from the clutch it will engage and the compressor will run. There is no way to diagnose this system with out a wiring diagram. A scan tool would also be vary helpful. Try, they may have the wiring diagram you need.
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