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  1. #1

    1997 Polaris sltx "limp mode" questions

    I bought this ski last year and I started getting a "HOT" alarm on the display which would shut down the rpms to 4200 and flash red for a few minutes but would run normal again after about 2 minutes, then repeat after about 3 minutes of running normal. The ski sat up for a year or so from previous owner so I figured the temp sensor was bad cuz the engine was NOT hot and I could rest my hand on it. I ordered a new temp sensor but never installed it cuz the problem stopped, so I figured the sensor was sticking due to not being used for so long. Then one day while riding it went down to 4200 rpms again only NO alarm displayed. The ski stays in this "limp mode" with no alarms until I tried it with the mfd unplugged. She runs perfect with the mfd unplugged but I don't want to leave it like this. Any help is greatly appreciated.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    Does the MFD display work normally?

    Clear LCD indicators showing clock, RPM, fuel and oil, etc?

    Is there any signs of moisture inside the MFD?

  3. #3
    Yes everything seems fine with the mfd and looks perfect. This ski was very well kept and everything on it looks like brand new. No moisture what so ever and after the HOT alarm stopped everything about it was perfect for a couple months. All of a sudden it shut down to 4200 rpms with no alarm, and even came back to normal at random intervals on my way back to the launch one day. Figured it was bad plugs. Changed them and next trip it just stayed at 4200 from that point on until I unplugged the mfd.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by japjrthib View Post
    Yes everything seems fine with the mfd and looks perfect. This ski was very well kept and everything on it looks like brand new
    Since you have a spare temp sensor I suggest installing it.

    While you are doing so, inspect for frayed wires and make sure the electrical box is clean and dry inside.

    Disconnect the battery while working on the electrical system.

    The HOT warning system is quite simple. The temp sensor grounds the Tan wire wire it gets too hot. The engine CDI and the MFD both watch for the Tan signal being grounded. The MFD shows the HOT warning and red flashing LED, while the CDI triggers RPM limit mode.

    It is unusual for RPM limit to occur without the HOT warning.

    On some models the MFD itself can trigger RPM limit due to low fuel or low oil. I don't recall from memory whether this applies to your 1997 SLTX.

  5. #5
    The "no alarm" thing is what's stumping me. I did remove the cover from electrical box and all looks fine. Can I disconnect the temp sensor wire and check if it runs right before completely installing the new temp sensor? Seems I have to take the whole exhaust system off to change that. It's very tight in there and I'm not a mechanic by any means.... Seems as tho that wire was already changed also. It's a blue wire now with a sticker on it that says "tan". Also the oil and fuel gauges are working perfect as I added both and the levels changed on the display.

  6. #6
    Quote Originally Posted by K447 View Post
    Quote Originally Posted by japjrthib View Post
    Yes everything seems fine with the mfd and looks perfect. This ski was very well kept and everything on it looks like brand new
    Since you have a spare temp sensor I suggest installing it.

    While you are doing so, inspect for frayed wires and make sure the electrical box is clean and dry inside.

    Disconnect the battery while working on the electrical system.

    The HOT warning system is quite simple. The temp sensor grounds the Tan wire wire it gets too hot. The engine CDI and the MFD both watch for the Tan signal being grounded. The MFD shows the HOT warning and red flashing LED, while the CDI triggers RPM limit mode.

    It is unusual for RPM limit to occur without the HOT warning.

    On some models the MFD itself can trigger RPM limit due to low fuel or low oil. I don't recall from memory whether this applies to your 1997 SLTX.
    So thers no way the mfd circuitry could be at fault beings that there's no alarm yet the rpms won't go past 4200 unless it's unplugged? Possible CDI problem perhaps? But why unplugging the mfd fixes it??

  7. #7
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    The only way the MFD circuitry could have anything to do with it is if there is something shorting the tan wire to ground either in the harness to the MFD or withing the MFD itself.

  8. #8
    Quote Originally Posted by BryanP View Post
    The only way the MFD circuitry could have anything to do with it is if there is something shorting the tan wire to ground either in the harness to the MFD or withing the MFD itself.
    the only thing I'm able to confirm is that the "now blue wire with the tan sticker on it" inside the electrical box looks fine and no frays or breaks in it, and no visible signs of abuse on the wire run as far as I can visibly see as I trace it to the exhaust manifold (or wherever it's connected to cuz I can't see it where the actual spring loaded sensor is plugged in). It's all sealed and neatly tucked in wire loom. I haven't removed the mfd or opened it up. I just unplugged the plug from the back of it and she ran like a champ when I did that. Do u know if just cutting/unplugging that blue/tan wire and plugging in the mfd to test again would let me know for certain it's that temp sensor even without it giving an alarm? Also, IF a grounding issue like that was the case, wouldn't it still give an alarm???

  9. #9
    Anyone? Anything? :/

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by japjrthib View Post
    Anyone? Anything? :/
    Sometimes you need to be patient. It is after midnight in EDT

    Since the MFD is directly connected to the Tan wire it is possible that a partial fault inside the MFD is triggering a marginal condition in the CDI for RPM limiting.

    Looking at the wiring diagram for the 1997 SLTX shows a single diode on the electrical box terminal board which isolates the MFD (and temp sensor) from the CDI except when the Tan wire signal voltage is lowered. Normally the Tan wire is fully grounded, either by the Temp sensor or by the MFD. A partial grounding potentially could allow the CDI to RPM limit while the MFD shows nothing.

    The easy test is to disconnect the MFD's Tan wire while leaving all other wires connected, and main MFD connector plugged in. If the problem goes away then the MFD itself is signalling the RPM limit.

    To confirm, reconnect the MFD Tan wire and unplug the temp sensor Tan (relabeled Blue) wire.

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