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Thread: Fans cutting in early

  1. #1
    apriliaforum newb
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    Fans cutting in early

    Hi all. I have an issue with my cooling fans. Up until a few months ago the fans would cut in at 95C and off again at ~90C. Now for some reason, they are coming on at 80C and off around 75C.
    Can anyone explain why this has happened and how to revert back to the previous temps? Thanks, Brad.

  2. #2
    apriliaforum expert kzmille's Avatar
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    There is either a problem with the temp sensor that feeds the instrument panel or related wiring or there is a problem with the thermo switch that turns them on. The two systems are totally separate so the fans might be working normally and your dash reading is off or the dash reading is correct and the thermo switch is bad. I think the later is less likely as the failure mode of the thermo switch is not usually closing at too low a temp.

    Both the sensor and switch are tested in a similar fashion with a pot of boiling water and an ohmmeter. Procedures are in the aprilia service manual.
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  3. #3
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    Thanks kzmille. I wasn't sure if the fans were controlled directly or if the temp sensor relayed the info to the ecu and that then controlled the fan operation - and hence maybe an ecu issue.

  4. #4
    apriliaforum expert JCG's Avatar
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    Quote Originally Posted by kzmille View Post
    There is either a problem with the temp sensor that feeds the instrument panel or related wiring or there is a problem with the thermo switch that turns them on. The two systems are totally separate so the fans might be working normally and your dash reading is off or the dash reading is correct and the thermo switch is bad. I think the later is less likely as the failure mode of the thermo switch is not usually closing at too low a temp.

    Both the sensor and switch are tested in a similar fashion with a pot of boiling water and an ohmmeter. Procedures are in the aprilia service manual.
    Likely the the thermo switch. They are suspect in infrequent cooling system flushes an long sitting times. I have mine on a switch now just because I'm to lazy to replace it....
    Chris
    What kind of bike is that?
    It's an Aprilia!!!
    Who makes them?
    .......... lets go of clutch lever.

  5. #5
    apriliaforum expert kzmille's Avatar
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    Quote Originally Posted by SheepBotherer View Post
    Thanks kzmille. I wasn't sure if the fans were controlled directly or if the temp sensor relayed the info to the ecu and that then controlled the fan operation - and hence maybe an ecu issue.
    No, the ECU is lot in the loop as it is on gen 2 bikes.
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  6. #6
    Honest always, feared often Micah / AF1 Racing's Avatar
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    On the Falco? Pretty sure of the temp senders one feeds dash information, one feeds UCU information and the thermal switch on the coolant manifold takes car of actually connecting fan operating point for turn-on and shut-off?
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    Micah Shoemaker
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  7. #7
    apriliaforum expert kzmille's Avatar
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    Yup, all correct as per gen 1 Mille.
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