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1997 Chevy Lumina 3.1 - Compressor wont enage
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dmcconnell
User
Jul 25, 2012, 10:02 PM
Post #26 of 27
(2679 views)
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Here is the wiring diagram from the book I have. A few things to note...
Light green goes into PCM from the AC Control Head. I believe this carries battery voltage into PCM when the control is set to Max, Norm, or Defrost.
AC Refrigerant Pressure and Coolant Temp both send a signal to PCM, Red/Blk and Yellow. They carry a resistance signal to PCM supplied through 5v, I believe I can test their input right at PCM.
AC Clutch Relay output is a ground through DrkGreen/White.. its my understanding that, when PCM receives a request, as long as all the other settings are correct (ECT, AC Refrigerant Switch, as well as IAT and TPS, which isnt in this diagram, but I am positive is involved elsewhere) it provides a ground circuit for the Dark Green/White wire coming from the AC relay.
... How does that sound? Correct? Any corrections?
If so I can rule out PCM by seeing if there is a ground circuit after PCM, and trace the wire back to relay. I can also test for battery voltage at the Pink wire into PCM to make sure the control head is sending signal to PCM. Which would make testing everything very simple, unless its inside the PCM, meaning I have to find out what is preventing activation from inside PCM.
I guess I have a lot of work to do tomorrow. A BIG thanks to my buddy johnbkobb who took an hour of his time today to call and explain quite a lot to me. It is a big help and I just may get this sorted tomorrow.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 26, 2012, 3:30 AM
Post #27 of 27
(2665 views)
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Although i can't really read anything on that scan, I can see it is a complete chassis diagram and includes all kinds of things unrelated to the A/C circuit. The diagram i posted was A/C circuit only. The only time CTS or IAT will have any effect on compressor operation is if they happen to be open circuit or full high voltage which would create a whole new set of problems unrelated to the A/C that would leave you with no doubt of the issue and there is no reason to consider an issue like that at all. It doesn't even look at TPS ever. It looks at engine RPM over time.
You need to just stop making this a whole lot more complicated than it is. Put a scan tool on it, see the A/C request, the current pressure reading from the pressure sensor and whether the PCM is turning the relay on or not.
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(This post was edited by Hammer Time on Jul 26, 2012, 4:04 AM)
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