Quote:
Originally Posted by foamypirate
I know I'm not TR65, but it sounds like my A/C setup (wiring/PCM wise) is pretty much the same as his. I have a factory 05' (Sierra Denali) pressure transducer in my compressor discharge line. Like TR65 mentioned, it controls only the fans, since you need a serial request for the computer to control the compressor. The PCM will still see the pressure in the system and run the fans without the A/C request signal.
As far as the pressure fault goes, there is a high/low pressure protection system built into the PCM. If the A/C pressure goes too high or too low (low is normal, just cycling the compressor on/off to prevent freezing the evap), the PCM will turn off the compressor. It will also cut off the compressor with WOT. Since we lose PCM control of this, you would need a low pressure and high pressure switch in the system, wired in series, to cut off the compressor in these situations. In my case, I used the factory low pressure switch (88' squarebody crewcab), and my replacement Denso 10S17F had a high pressure switch in the back of the compressor body (which cuts out at 455psi). So, I have 12v from the factory control head, through the low pressure switch, through the high pressure switch, to my relay, which controls the 12v+ side for the compressor. If any of the switches goes open, my compressor shuts off.
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Thanks for the info. Does your compressor come on and stay on until you turn it off? Mine isn't it's cycling on and off and I assume it is being controlled by the computer, which would lead me to believe that it has some over/under pressure protection that is being provided by the PCM. But I would like to be certain because I don't want to damage anything. Thanks again. FYI, I'm using a 2006 Tahoe P59 PCM. More info here:
http://67-72chevytrucks.com/vboard/s...=709611&page=2