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Thread: F800 ST fan thermal switch

  1. #1
    Day Dreaming ... happy wanderer's Avatar
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    F800 ST fan thermal switch

    Anyone replaced one of these yet? A friend fried his accidentally and BMW only sells the entire fan assembly. I am looking for schematics or an alternative thermal switch for his perfectly fine (tested it) fan!
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  2. #2
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    I haven't done any work aside from basic maintenance on an F-bike but I make my living fixing cars. Are you certain that the fan control thermo-switch is part of the fan assembly? I don't have an ST around to look at but typically the thermo-switch is either screwed into the radiator or, more commonly now days, vehicles simply use an input from the engine temperature sensor, the ecm then activates a relay for the cooling fan. (peeking at my 800GS I don't see a switch at the fan or radiator but again I'm not very familiar with these F-bikes yet). Is it possibly a relay that has fried and not a switch?

    Let us know what you find and how you fix it.
    1970 R75/5 Old Faithful
    2013 F800GS New Flame

  3. #3
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by bustedknuckles View Post
    I haven't done any work aside from basic maintenance on an F-bike but I make my living fixing cars. Are you certain that the fan control thermo-switch is part of the fan assembly? I don't have an ST around to look at but typically the thermo-switch is either screwed into the radiator or, more commonly now days, vehicles simply use an input from the engine temperature sensor, the ecm then activates a relay for the cooling fan. (peeking at my 800GS I don't see a switch at the fan or radiator but again I'm not very familiar with these F-bikes yet). Is it possibly a relay that has fried and not a switch?

    Let us know what you find and how you fix it.
    There is a small rectangular plastic box mounted on the fan shrouding. Fan power wires go in and out of it. Dissection revealed two wound coils, one electrolytic capacitor and the rest was too burned to recognize. Since it is right above the heat source and it's position on the shroud in the absence of any schematics I am assuming it is a thermal fan switch.

    The fan spins no problem connected to a battery. BMW does not sell the switch (or whatever it is) as a separate part, they will only sell the entire fan assembly. BMW Part 17 11 8 528 880. $245 at Max BMW. If you could see the part in the fiche it's on top behind the power connector.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  4. #4
    Outlander Omega Man's Avatar
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    I too try fixing the un-repairable Try this place- http://www.mouser.com/ they have an extensive catalog and since you can see it, you might be able to match it up.......Possibly with a thermistor/relay set-up. If you are doing a bit of re-engineering, you can always incorporate an "always on" switch- just in case. Good luck. OM
    "Well they say.. time loves a hero but only time will tell.. If he's real, he's a legend from heaven If he ain't he was sent here from hell" Lowell George
    2009 F800GS 1994 TW200
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