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Thread: Idle Air Control Valve Questions

  1. #1
    The Brown Blob 87gtVIC's Avatar
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    Default Idle Air Control Valve Questions

    Was reading that some cars have a diode in the wiring leading to the IAC and that replacement IAC's may come with the diode already installed internal to the unit and that removing the factory diode from the harness is suggested.




    http://vb.foureyedpride.com/showthre...0593-86-Gt-5-0


    Anyone hear something like this?
    ~David~

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  2. #2
    Beater gonna beat sly's Avatar
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    First I've heard of it. Don't know why you would remove the diode as it would essentially work as a backup in case the other failed.

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  3. #3
    I'm an air-conditioned gypsy gadget73's Avatar
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    never heard of it but I just had a look in my 86 and 91 EVTM. The 86 book shows a diode in parallel with the IAC. The 91 book shows an IAC with an internal diode.

    Its a flyback diode. The only thing it does is conduct when the power is removed from the coil in order to keep it from back-feeding a spike of voltage. No reason you can't have two in parallel. Its not dropping any voltage or anything of that nature. Only real argument I can make for removing it is that if the one in the harness goes bad it will act like a bad IAC and replacing the IAC won't fix the problem. Never honestly heard of anyone having that problem and diodes are like 10 cents so NBD.

    86 Lincoln Town Car (Galactica).
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  4. #4
    The Brown Blob 87gtVIC's Avatar
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    Cool. Just wanted to bring this question to this forum and see what feedback comes of it.
    ~David~

    My 1987 Crown Victoria Coupe: The Brown Blob
    My 2004 Mercedes Benz E320:The Benz

    Quote Originally Posted by DerekTheGreat View Post
    But, that's just coming from me, this site's biggest pessimist. Best of luck

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