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Thread: General IAC Info & Ford PWM IAC Wiring

  1. #11
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    Quote Originally Posted by kbscobravert View Post
    Does the Ford IAC care which of the 2 wires is the PWM+?
    Yes, some have a built-in diode clamp to prevent reverse polarity. Look for the small "+" & "−" symbols on the connector.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  2. #12

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    I'm having a little problem trying to figure out which is the positive and which is the negative. I'm using the Mass-Flo EFI and it has the early version of the IAC motors that you showed in the opening post. I ordered a replacement connector from Standard, but the part isn't marked which terminal is which. Could someone tell me which one is which?

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  3. #13
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    Quote Originally Posted by jeff@califon View Post
    I'm having a little problem trying to figure out which is the positive and which is the negative.
    I don't know because I don't use that type of IAC motor. But can't you figure it out from the prior Mass-Flo wiring?
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  4. #14

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    I will have to dig out the manuals and look for the wiring diagram. Hopefully it shows some sort of detail.
    I think I found it. Scroll down, the connector is shown open end, and the locking tab is visible.


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  5. #15

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    From the diagram, it looks like the pin next to the locking clip on the plug, is key on +12V, and the ground is what is controlled by the ECU. That changes things.
    Last edited by kbscobravert; 11-10-2014 at 05:56 PM.

  6. #16
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    Yes, on a Ford, the IAC gets constant +12V (ignition key on) power, and the Ground is controlled by the ECU using a PWM− signal at 300 Hz.
    The Holley can control it by PWM+ with a Ground tied to the engine block, or it can get a +12V power source and control it with a PWM− signal.

    In my personal experience, the Ford IAC, because of how it operates, will be more stable & perform better, if you supply it with a constant +12V
    signal and a PWM− from the Holley ECU. I do not know why it works better, I just know we have tried it both ways, and it has always worked
    better using a PWM− signal to control it. Also, in my personal experience, if you can use a GM IAC, it always works better than the Ford IAC.
    Last edited by S2H; 11-10-2014 at 11:05 PM.
    -Scott
    Don't forget to check out progress on my Race Car:
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  7. #17

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    Quote Originally Posted by S2H View Post
    In my personal experience, the Ford IAC, because of how it operates, will be more stable and perform better, if you supply it with a constant +12V signal and a PWM- from the Holley ECU. I do not know why it works better, I just know we have tried it both ways, and it has always worked better using a PWM- signal to control it.
    Thanks, I will connect it as you suggested. I discovered which terminal was which by using the diagram, and verified that using a 9 volt battery.

  8. #18

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    Resurrecting this one. I'm going to use the Ford IAC PWM−, and was wondering if I can re-purpose the pins/open slots from the original IAC wiring, in the ECU, to make a different I/O.

  9. #19
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    Quote Originally Posted by one5oh2nv View Post
    I'm going to use the Ford IAC PWM−, and was wondering if I can re-purpose the pins/open slots from the original IAC wiring, in the ECU, to make a different I/O.
    Yes, you can relocate one of the existing four wires (stepper IAC motor) to an available custom I/O position.
    Installing, removing & relocating (pinning) the ECU connector terminals is easy. No special tools involved.
    Push the single wide white tab to release the lock (on all terminals), and push the two narrow white tabs to re-secure.
    http://forums.holley.com/showthread....neral-IAC-Info (IAC Information)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #20

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    FYI: If you are looking for the connector for '87-'93 Mustang IAC, here's an alternate source:
    http://www.oreillyauto.com/site/c/de...1517&ppt=C0189 (BWD - Electrical Connector PT317)

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