2007 Sportster Idler Air Control Issue

Discussion in 'Electrical' started by Flatliner1775, Sep 27, 2010.

  1. Flatliner1775

    Flatliner1775 Member

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    :34:I noticed that the IAC is running when i turn the key off and is draining my battery. Can this be a short in the IAC itself?
     
  2. Hoople

    Hoople Account Removed

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    Are you sure what you are hearing is the IAC.


    The IAC stepper motor actually does not "run". It normally does run for a second or two when you first turn the key on. It then goes to a pre-determined step position which it pulls from a "warm up IAC" stepper motor map.

    Even though it is called a motor, it does not run or turn around and around like a normal motor does. It will step Forward to a position or limit position. Then it runs (steps) backward to a limit position. That's all it can do is run forward and then backward a bunch of steps. And to step forward or backward requires a micro-controller with software. You can't just hook the IAC motor to a battery and watch it turn or spin.... so I doubt that is what your hearing.
     
  3. Flatliner1775

    Flatliner1775 Member

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    Hoople,

    That is what I am hearing. After doing more research I found this:

    MOCO Service Bulletin Ref TT322 – July 26, 2007

    July 26, 2007 - 2007 XL Models with Discharged Batteries or Very Low Voltage 2007 XL Models with Discharged Batteries or Very Low Voltage

    Harley-Davidson has found some ’07 Sportsters where the batteries are going dead after a night of sitting. The root cause is water intrusion. Water can run down the harness, funnel into the fuse block area, and then bridge the system relay contacts. The system relay has constant power available on the 30 terminal.
    When the system relay is activated, power goes to the ECM, and then the ECM sends power out to the IAC. The IAC will then run until the battery is fully discharged.
    To prevent this issue, Electrical Contact Lubricant (p/n 99861-02) can be placed on the terminals and base of the system relay, and the receptacles at the fuse block. This will create a water barrier once the relay is installed into the fuse
    block.
    Motorcycles exhibiting this condition could also have corrosion present, and if necessary, should have the relay terminals and receptacles cleaned with a wire brush or replaced.
     
  4. Hoople

    Hoople Account Removed

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    If you really want to know the truth, HD is incorrect. The ignition switch & Kill switch turns on the ECM. The ECM then turns on the system relay. It's not the other way around. Plus the fact the software has to loop to make the IAC step is too hard for me to believe. Trust me, it's an oversight in whoever wrote the service tip.

    But that really does not matter right now because you can perform a simple trick to figure out what really is going on.

    While you hear this "stepper buzzing", pull the system relay and see if the buzzing stops.

    (The system relay turns on the electric fuel pump. I think that is the buzzing you hear. Like I said, you just don't apply power to an IAC motor and watch it step. It requires software to make an IAC rotate. Is HD telling me the ECM booted up and is stepping through the assembly code.)
     
  5. Flatliner1775

    Flatliner1775 Member

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    I know its the IAC making the sound. I unpluged the IAC and the sounds went away. Now when I get home I will have to look at this relay they are taking about. But it looked like someone had the same issue on this fourm and this was the relay.
     
  6. Hoople

    Hoople Account Removed

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    Maybe the 2007 Sporty uses the system relay in a different way than the Dyna models like mine does (?)
    On my bike it is physically impossible for a short in the system relay to boot the ECM, without also having the Kill switch in RUN and the ignition turned on. Looking at my schematics, the IAC stepper is driven off the ECM and not the system relay. There is no telling what they did different from a 2007 Sporty to a 2009 Dyna. ..

    It sounds like you nailed down your problem and saved yourself a bunch of time & money. A leaky system relay WILL drain a battery. I have to print and save that tip.
     
  7. orgredneck

    orgredneck Member

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    Re: Sporty Eating Batteries

    Had this happen to my 08 sporty.
    With key off listen behind air cleaner
    for IAC engaging with key off.
    System relay was coroied and feeding IAC.
    With key off killed battery overnight.
    cleaned fuse box and new system relay fixed problem.
     
  8. Flatliner1775

    Flatliner1775 Member

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    Yep. I pulled the relay and check it. It was stuck closed. Going to head to the HD parts store and get a new relay. orgredneck how much did it cost?
     
  9. nvsteve

    nvsteve Member

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    There was a change in the IAC in 08 I believe. On my 07 you can see the valve inside the throttle body outside the butterfly in the 12 o'clock position.
    After 07 it's in a different place. Not sure if there was an electrical change as well.
     
  10. Hoople

    Hoople Account Removed

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    Thanks! That just may be it. Until I come across a set of schematics for a 2007 Sporty, I will be scratching my head. I need to know why & how a shorted system relay could possibly cause an IAC stepper to Buzz.

    Maybe just maybe a stepper motor was not actually used on that year/model. An ordinary servo motor could have been used also. That would explain the entire phenomenon to me. I bet that's what it is because source power would then come off the System relay.