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Which wire from ECU handles AC Clutch relay?

Discussion in 'ECU's, Electronics, and Tuning' started by Raggedyman, Jul 9, 2003.

  1. Raggedyman

    Raggedyman Member

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    I've gone by all the articles I can find both here and elsewhere, and I can't seem to find what ecu wire controls the AC clutch relay. I swapped in a '95 D16Z6 into a '90 hatch (std), using a '91 Si ecu (PM6) to control it all, but according to the pinouts the wire that should pull in the AC clutch relay is now used by the fast idle valve.... B3. The Si version calls for both B7/B8 to be used together for the AC switch, but there's nowhere for the clutch relay wire.

    I've grounded the wire going to the clutch (yellow wire that came from B3 when I put the fast idle control in it's place), and it pulls in as soon as I turn on the fans...no matter if AC is on or not. I've tried a couple of other ecu connections but none give me the ground that I need to pull it in on a timer basis as it should be.

    Should I just pull the fast idle control valve off B3 and put the ac clutch relay back on it? Or do I have something else miswired? The car runs strong and has no hesitations at all. Everything else works great too with no problems.

    Thanks for the help!
     
  2. jlicrx

    jlicrx Senior Member

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    pm6 ECU - my diagram shows - B2, (blue) fast idle control valve - B3, (yellow) a/c compressor clutch relay - B4, (yellow/green) a/c on input - B7, (green) a/c on input - B8, (blue/red) radiator fan and condensor fan control
     
  3. Raggedyman

    Raggedyman Member

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    Thanks...I tried those but I still can't get the compressor clutch to pull in right. With that wiring it won't pull in at all. Might be a bad timing relay but I hope not.....
     
  4. blundar

    blundar Senior Member

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    you try manually engaging it by connecting the clutch directly to +12v and bypassing the ECU? Not all ECUs have the circuitry to control AC. It's an option on the ECU just like on the car.
     
  5. Raggedyman

    Raggedyman Member

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    I've manually grounded the old wire from the old ecu and the clutch pulls in, but it never lets go. Originally, the system was a positive feed to the clutch with the negative switched at the ecu. That was my old ecu for the D15 engine I had in it. Since I've done the swap (complete engine, not just the head) with the D16 and the pm6 ecu, I can't find where to land that clutch wire. The Si must be doing it differently and switching the delay timing relay or something that I can't figure out. With the wire manually grounded, not even turning off the ac switch will release the compressor clutch. Gonna keep trying though.... :)
     
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