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  1. #1
    hill160881's Avatar
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    Arrow Common failures of System Interface Box (SIFB) on MSX 150 and MSX 110

    What is this item people try so hard to get?
    Last edited by K447; 06-20-2014 at 10:11 PM. Reason: Thread title


  2. #2
    hill160881's Avatar
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    Found a thread that explained it. Now, How to bypass it if in the event it goes out on the water. Consider I live on 1200 miles of water channels and could be up to 100 miles from my marina at any time.

  3. #3
    ripcuda's Avatar
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    From the service manual:
    System Interface Box (SIFB)
    The primary function of the SIFB is to power--down the ignition system in the event that the lanyard is left inserted
    in the stop switch for more than two minutes. Without the SIFB, the ignition system would remain powered--up
    by the battery, and the battery would completely discharge.
    A secondary function of the SIFB is to convert the reverse switch signal so the ECU can interpret the signal when
    the reverse switch is closed, thereby limiting engine RPM.
    These are the most common failed electrical part on Webers (not counting oil fouled MAP sensors). Polaris hasn't had any new ones for sale for years. Only ones you could get were used off parted-out skis... thus they were highly sought after.

    Finally, the aftermarket came through last year and a manufacturer that Randy worked with got some new ones made. I helped test the prototypes. The news ones for sale now (Marto sells them) removed the auto power-down feature... so lanyard in = powered up, lanyard out = powered down... gotta pull the lanyard or you'll drain the battery. Reverse function still works.

    FYI... I've heard of a bypass... but never seen or read of anyone successfully bypassing the SIFB. Would love to know if possible.

    Cheers!

  4. #4
    ripcuda's Avatar
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    Oh... and common failures of the SIFB can cause:
    - failure to be able to shut off the running engine... even with lanyard out (happened to me)
    - ECU 3400rpm rev limiting forward (instead of reverse)
    - ignition system not powering down after 2 minutes (sometimes even w/ lanyard pulled)... drains battery
    - ignition system not powering up... thus can't start
    - probably others too...

    Cheers!

  5. #5
    hill160881's Avatar
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    Thanks much. This information should be stickied if not already and I missed it again.

  6. #6
    GGG's Avatar
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    I had recently bypassed on but i was still having problems with the ski and being i dont have digital wrench, i dont know if my bypass was one of the reasons the check engine light was on

  7. #7
    Moderator HiPeRcO's Avatar
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    Quote Originally Posted by ripcuda View Post
    Oh... and common failures of the SIFB can cause:
    - failure to be able to shut off the running engine... even with lanyard out (happened to me)

    Cheers!
    This is a serious safety issue...has anyone (ideally an owner with the problem) ever reported it to the proper government authority? Polaris should be forced to do a recall on these...

    Anyone ever ponder a secondary kill switch somewhere (elegantly connected and located)? I'd hate to have a kid or an inexperienced rider on one of these when it couldn't be shut off.

  8. #8
    ripcuda's Avatar
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    Quote Originally Posted by HiPeRcO View Post
    This is a serious safety issue...has anyone (ideally an owner with the problem) ever reported it to the proper government authority? Polaris should be forced to do a recall on these...
    Guess I never saw it as a safety issue... just an annoyance. It's not like unintended acceleration or the brakes didn't work. The ski just sat there and idled. I've heard more issues of failed SIFBs causing rev limiting issues (SIFB tells ECU reverse is on when it's not)... and starting issues... then the odd failure to shut-off issue I experienced.

    Anyone ever ponder a secondary kill switch somewhere (elegantly connected and located)? I'd hate to have a kid or an inexperienced rider on one of these when it couldn't be shut off.
    Suppose you could. I just fixed the SIFB and never had a problem again. I'd be careful of where you might locate an additional kill switch. Wouldn't want it somewhere it could accidentally be triggered (like if it was in the glove box or something). A shut-off engine at WOT or during evasive maneuvers sounds dangerous.

    Cheers!

  9. #9
    Moderator HiPeRcO's Avatar
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    The machine will stay running with the lanyard unplugged, like when you fall off...ski then becomes a zombie ski, and could end up miles away...

  10. #10
    would this explain why my ski does not accelerate? it starts fine. idles fine. but when i apply the throttle the engine barely responds. the ski dose not run when the kill switch is pulled out of the connector.

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