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Thread: 411 PCM AC request

  1. 01-18-2011 #1
    Efi69Cam
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    411 PCM AC request

    Want to integrate 12200411 PCM control of the AC compressor with my vintage air system. The VA system provides ground for the relay coil. Looking at the wiring diagram for a 2002 Corvette it looks like the ac request pin on the PCM is grounded by the ac controller (manual control) however on 2002 camaro schematics it looks like the ac request is switched to +12. Which is correct, or does it depend on the base calibration in the ECM? I'm using Corvette for the ETC.
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  2. 01-20-2011 #2
    DrLoch
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    I have done a 411 PCM convert, my AC request (Red 43) is to 12 ground through a relay.
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  3. 01-20-2011 #3
    u00bse1
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    Some of the ECM pins are VIN dependant. Be carefull comparing these on the 411. Use one wire schematic that matches a known VIN only.
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  4. 01-20-2011 #4
    Efi69Cam
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    thanks for the info.

    I will be using a 2002 Corvette Z06 VIN to get the base cal in my PCM. Seems that I need to make sure the VIN has manual AC instead of the serial.


    So the answer is it depens on the calibration- it could be +12 or ground switched?
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  5. 01-20-2011 #5
    Sam88gta1
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    You can use a relay to control the VA through the pcm with either 12v or ground.
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  6. 01-21-2011 #6
    flame
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    Do you need the A/C pressure reading input to allow the PCM to control this?
    1997 Trans Am WS6 - LS1 swap - TR224 - Pacesetter Longtubes - Yank SS3600
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  7. 01-21-2011 #7
    Efi69Cam
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    Quote Originally Posted by flame View Post
    Do you need the A/C pressure reading input to allow the PCM to control this?
    From what I've gathered from reading the service manuals, yes the pressure sensor is needed.

    The PCM and pressure sensor together act like the trinary switch with the added benifit of taking road speed and other factors into account. Additionally you can set the RPM and TPS shutoff and resume points in the PCM with the HPTuners.

    My confusion lies with the apparent differences in what the PCM is looking for as an AC request signal with the various factory calibrations. Looks like the corvette uses a ground to activate and the truck and f-car cals looks for a +12. The ground is ideal for the Vintage Air system.

    For others wanting to do this I got what seems like a solid answer about the Corvette setup from this thread.

    http://www.ffcars.com/forums/showthread.php?t=85929
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  8. 01-21-2011 #8
    flame
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    Quote Originally Posted by Efi69Cam View Post
    From what I've gathered from reading the service manuals, yes the pressure sensor is needed.
    That is what I have figured too and have never had the chance to try without but the above posts made it sound like they could.....
    1997 Trans Am WS6 - LS1 swap - TR224 - Pacesetter Longtubes - Yank SS3600
    - 3.42 Moser 12 bolt - Wilwood Brakes - HP Tuners tuned - P1SC-1 Procharger
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