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Thread: A/C install in 1993 rx7 ls1b pcm

  1. #1
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    Default A/C install in 1993 rx7 ls1b pcm

    Hey everyone!

    I have a 1993 mazda rx7 with 402ci ls2 and I'm running the LS1B 2001 fbody PCM. The car runs great, but I installed AC into the car and now I'm having all sorts of problems with getting the compressor to stay on. Once I flip the AC request on, the compressor stays engaged for only about 5 seconds then turns off. It is not hitting the AC pressure cutoff value (yes) before it shuts off. If I force the compressor and fans on via EFIlive the pressure gets to 3.1v and stays, but the high pressure cutoff flips to yes at 2.8v which is wrong as the manifold pressure high side is only 220psi.

    Is there a way to change the high pressure cut off values for the ac pressure sensor? This can be done in HPT somehow but I can't find it in EFILIVE.

    Also I'm monitoring state00 and I don't see any reason for the compressor to disengage after 5 seconds, any ideas why it would be disengaging? I don't see parameters for the AC clutch engage like rpm under AC parameters, where can I find all of the parameters?

    Sorry new to EFILIVE but I'm stumbling through it. The car is already tuned, I just can't get ahold of my tuner for support/help with this. When it was tuned the car did not have ac so is there something he might have changed?

    Thanks Ryan

  2. #2
    Joe (Moderator) joecar's Avatar
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    Post your tune file.

    Which ACP sensor do you have...?

    How is it wired to PCM...?

  3. #3
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    Pin 18 red connector is getting the sensor volts. Then it has 5v reference and ground. I'm using the gto ls2 sensor but i ordered the fbody one to see if they are different.

    I'll post up the tune when i get home. Thanks for the help so far.

  4. #4
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    I found that the ac delco part #s are different but they look identical so i don't know if they read different.

  5. #5
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    Ok here is the tune file attached.
    Attached Files Attached Files

  6. #6
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    My new pressure sensor came in today and i installed it. Now the volts are reading lower and the high pressure cutoff field is not hitting yes. So that fixed the high pressure problem. But i have to force the compressor on. Otherwise if i request it the compressor will turn itself off 4 seconds after turning on. Every time. It's very strange.can someone please take a look and see what could be causing this?

  7. #7
    Joe (Moderator) joecar's Avatar
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    Do you have it wired like this (attached 2001 F-car diagram)...?
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  8. #8
    Joe (Moderator) joecar's Avatar
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    The only A/C tables I see different than the stock 2001 F-car are G0107 and G0109.

  9. #9
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    I GOT IT!! My harness is missing the pin 18 red connector 12v that comes from the compressor clutch relay and shows up as A/C status in EFI LIVE. I thought it was just a field that the PCM monitored so it could throw a MIL if it didn't see it, but apparently the PCM needs to see it in order to keep the clutch engaged. I put 12v to it when the AC request activates and the compressor works just as it should. Finally figured all of this out, now I just need to buy some PCM wiring pins. Any idea where to get one or two cheap?

  10. #10
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    For a LS1 PCM? EFIConnection I know sells them but not cheap for just a pin.

    Let me check tomorrow and see if I have one, if not it might be easier to grab a PCM off eBay with the connectors and pull a pin that way. I'll check back in tomorrow.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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