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Radiator Fan not working

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by davway, Sep 26, 2007.

  1. even though i am the only person here with this bike, i am hoping that someone can help me anyway.
    the bike in question is a 1984 Suzuki GS250FW.
    the radiator fan doe not seem to work at all. ive had the bike up to 3/4 temp and it still didnt kick in. i unplugged the fan and got a test light and it seemed the connection wasnt getting power. test light is a tad dodgey, but im still going to assume there was no power getting to the fan at all.
    ive only found 1 fuse on the whole bike and that was fine. it did however have a 30 amp fuse in it even though its only meant to have a 20 amp fuse. replaced it with a 20 amp fuse and everything still worked excpet the radiator fan. does it really matter if its a 20 amp or 30 amp fuse in the bike?
    what could be some possible reasons, or things that are easy to test for, to find out the cause of the fan not working?
    i havent fully explored this problem yet, wiring/electronics isnt my specialty so any tips, suggestions, solutions would be appreciated.

  2. Power the fan separatley to see if it does work. If it does you will need to find out how hot the coolant actually is (temp gauges can be flakey) at 3/4 if thats your comfort limit and find out at what temp the fan should cut in. If its under the 3/4 mark you have a switch issue.

    Side Issue, I would think 10amp would be plenty.

  3. to ask a dumb question.....how do i do that?
    it has a wierd connector on it and i dont have anything it would plug into.
  4. A bush mechanics way would be to run a couple of wires straight from the battery. You could run a fuse as well just to be on the safe side.
    There should only be 2 wires in the plug so shove the wires into the plug.
    It shouldnt matter if the fan runs forward or backwards all you are testing is if it operates.

    Like I said its rough but it may answer your question. Otherwise an autoelec could test it for a fee......
  5. thanks, ill give it a shot.
  6. That should be fine, altho I am not a Suzuki expert. It will only come on when the bike is ready to overheat.

    The fan will not normally have power to it unless the temperature sender has "tripped" and made a contact. The correct way to test it is to find the temperature sender which triggers the fan. It will be a round device about 10-15 mm diameter and about a cm high and is black plastic in a metal case, which has 2 electrical leads attached. It should be inserted in the radiator somewhere.

    Simply short these two wires and the fan should start spinning. Oh, you had better turn on the key as well. ;-)


    Trevor G
  7. why make it complex?
    stick with 2weels' idea. fail safe, and instant results ;)
  8. The fan, since it seldom runs, is unlikely to have failed, if anything has.

    On the other hand the sender/thermal switch is in use all the time, and is more prone to failure.

    In any case, shorting the leads on the thermal switch should turn the fan straight on. That's a lot easier than hooking up live wiring to the awkward fan terminal block. ;-)


    Trevor G
  9. thanks guys.
    hooked up 2 wires to the battery and the fan does work after all.
    must be sender that has failed.
    bike is sitting pretty at around 1/3 temp with the fan on.
    fan off and its been to 3/4 temp.
  10. Remember that the temp gauges are not accurate as to scale. There will be an overheat section to the right. If it does not get into there you should be OK.

    The average bike radiator fan of this era does not come on, even in the heat of summer, unless you are stopped with no airflow, as in idling for a long time. You would need air temps over 30C I reckon before you see the coolant reaching the high side after prolonged idling.

    Have you located the temp switch/sender?

    You can test it in boiling water - do not immerse it! - and then checking that the internal contacts "make". It's not easy to check if you don't have a multimeter. The switch would open again once you remove it from the water. The contacts will actually close or "make" before the water boils - it's handy to use a thermometer in the water as you do so, but most people these days don't have thermometers for liquid.

    I can't help wondering if you are not worrying about nothing. If the temp gauge is not going into the "red" or the solid area at the high end you should be OK.


    Trevor G