Fan not working on a 950

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by dongie, Jul 20, 2013.

  1. dongie

    dongie Brraaap

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    Hey guys, I wondered if any of you had an input to my issue.

    My 950 overheated and puked out a ton of coolant on a fairly hot day, after I ran it hard through the gears almost all the way to red line a few times. Maybe a 5min. ride. Quite strange if you ask me.
    I noticed that, despite the high engine temp, the fan wasn't on. I filled the cooling system back up and bled it as good I could. I also replaced the thermo switch (with the stock temp unit) as I expected that to be the culprit.
    I started the bike up, let it warm up to 5 bars, and the fan is still not kicking in.
    The fuse is fine and the fan works if I jump the connection in the fan plug.

    What gives?
    #1
  2. nomad guy

    nomad guy A legal alien

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    Try checking the wiring. Continuity between the fuse and the fan connector or even closer to the fan itself, check for 12v. Continuity between the thrmo swithch and the fan- brown-black wire. Check that the thermo switch wiring has continuity to ground- brown wire.
    Also, it might be good to double check that the thermo switch is coovered with coolant and that the switch is good. You can check the switch by covering it with boiling water and checking for continuity between the wire blades.
    #2
  3. dongie

    dongie Brraaap

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    Correct me if I'm wrong, but if the problem was in wiring, the fan would not turn on when I simulate a closed thermo switch by jumping the wires between the fan and the thermo switch. It works when I do so.
    I just installed a brand new switch and the issue wasn't solved.
    I bled the cooling system with the front wheel almost 2' in the air and the radiator seems to be full of fluid with no air bubbles. I squeezed the left rad hose a few times also.
    The water pump is about 5k miles old and the oil is coolant-free. The head nut washer upgrade was done about a year ago also.
    #3
  4. nomad guy

    nomad guy A legal alien

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    Your first post indicated that you jump the fan connector not the thermo switch. It is a basic electric circuit without any electronic components. It constantly hot when ignition switch is on. the thermo switch is switching the earth wire. So, follow the V and the earth when the bike is hot. check the new thermo switch for continuity when you have 5 bars. make sure none of the connectors is corroded or has broken or bent pins.
    #4
  5. dongie

    dongie Brraaap

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    Where is the water temp sensor located? Is it wired into the engine or into the radiator?

    I wonder if a bad thermostat would keep hot water circulating inside the engine and not allowing it cool off in the rad. If the temp sensor is in the engine, maybe the coolant in the rad doesn't get hot enough to trigger the fan?

    I guess it would help to let the engine heat up to 5/6 bars and check if the fan thermo switch is closing like you suggested.
    #5
  6. dongie

    dongie Brraaap

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    Just replaced the thermostat and bled the system again. The fan is still not coming on :scratch
    #6
  7. Head2Wind

    Head2Wind MotorcycleMayhem

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    Do you have a multi meter that can measure DC volts?
    #7
  8. dongie

    dongie Brraaap

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    A friend of mine is coming with one in a few hrs. I'm going to get the bike to 5 bars and see if the switch is closing.
    Do you suggest checking anything else?
    #8
  9. Head2Wind

    Head2Wind MotorcycleMayhem

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    As previously stated by someone else, with the ignition in a ON state, there should be battery vdc present if measured from on the POS of the fan terminals to the battery neg post. If running a standard fan thermo switch, the displayed bars (5^) will be required before the switch will close circuit (completing the GND circuit in this situation). If the bat VDC is there at the harness when sign swt is on, then the GND connection to the fan system is faulty. Quick way to test this is unplug thermo swt, and with ign on, then jumper between terminals on the thermo swt harness plug. Fan should run.

    Sent from ADVmachines.com via Tapatalk
    #9
  10. Orangecicle

    Orangecicle On a "Quest"

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    Probably off topic, but I know that there is a temp sensor on the rear jug. I learned about it after ripping the wiring out of it while removing the engine. :lol3 Does anyone know how this temp sensor interacts with the system?
    #10
  11. Head2Wind

    Head2Wind MotorcycleMayhem

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    The sensor at the rear cylinder is for the gauge on the dash, nothing to do with the fan control

    Sent from ADVmachines.com via Tapatalk
    #11
  12. dongie

    dongie Brraaap

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    Does my issue have something to do with coolant circulation then? We just tested the switch by heating it up over a stove and it did close the circuit at somewhere around 220-250 degrees.
    It just seems that the engine can get so hot it boils over but the coolant is still bellow 220 degrees?
    I just got it to 6 bars on the dash, with the coolant slowly starting to trickle from the overflow and the fan didn't move.
    #12
  13. Katoom72

    Katoom72 Been here awhile

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    Bleed the circuit and add a new radiator cap. If the system is not pressurised enough the coolant just starts to boil while the thermoswitch is not getting enough heat to trigger operation and close the electrical circuit.
    #13
  14. dongie

    dongie Brraaap

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    I installed a new cap last year and it still looks like new..
    #14
  15. dongie

    dongie Brraaap

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    Water pump not working properly? I tried to bleed the system twice with the front wheel up and I'm pretty sure there shouldn't much if any air in the system.
    Which brings me to a question - if the thermoswitch was okay, how come the bike boiled over so quickly in the first place? It ran perfectly fine for about a year since the last water pump rebuild and cooling system bleeding :huh
    #15
  16. nomad guy

    nomad guy A legal alien

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    How fast does it takes your bike to get 4 bars? on a normal idling bike it should take a few minutes.
    In regard to the thermo switch, after you confirmed that switch itself is working fine and you have continuity from the switch to the fan, you need to confirm you have continuity from the brown wire of the switch to ground.
    The only way to eliminate an electric problem is going through the whole circuit methodically.
    #16
  17. nomad guy

    nomad guy A legal alien

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    Oh, one more thing. Test the switch in boiling water not over a stove. The standard switch should close at ~216F/102C.
    #17
  18. dongie

    dongie Brraaap

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    It takes a while for the bike to warm up to 4 bars, certainly a few minutes just like it always has.
    I didn't check the continuity but if the circuit was broken, I believe jumping the connection in the switch socket would not turn the fan on? The fan does turn on when I jump the connection and bypass the switch. The fuse as also working properly as taking it out kills the fan (when running).
    #18
  19. nomad guy

    nomad guy A legal alien

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    Regarding issues that are not the fan, when the bike reaches 5 bars jump the thermo switch and let the fan run continually and observe if the bike manages to keep a steady temp, thus eliminating other cooling issues.
    #19
  20. dongie

    dongie Brraaap

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    It should be able to cool itself back to 4 bars while idling with the fan on, correct?
    #20