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Thread: Radiator fan not turning on

  1. #1
    Senior Member sugarrey's Avatar
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    Radiator fan not turning on

    So lately I have been having a "once in awhile" overheating issue. Well decided to see WTF if going on. Noticed that the bike got up to 240 and the fan just is sitting there, didnt even attempt to turn on. So I check the fuse and the fuse is good. Great....Ya know I love this bike, but lately it seems to be a lil too much, good news is I got nothing better to do than to work on it.

    So the bike is a 99 r1. I am going to dig into the manual and see what I can find. There has to be a switch of somekind somewhere. Also the blade are free from debris and should run completely un-obstructed. Screwed up part is that the fan is in between the motor and the radiator with about 1/8 of room where I can barely see, what a PITA!!!

    Any other suggestions or opinions?

  2. #2
    I'm pumped... Let's let the healing begin! Lifetime Supporter ~Barn~'s Avatar
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    Re: Radiator fan not turning on

    Even though the fuse passed visual tech, I'd replace it anyway, just to be certain.
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  3. #3
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Yeah I hear ya....Tried it and the fan still was dead.

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    Re: Radiator fan not turning on

    You could try wiring a switch. Usually the fan is negatively triggered in order to activate it. So in other words, once a common ground is available it kicks on.

  5. #5
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Yeah I know but I would really like to fix this issue correctly, I dont want to rig it up with manual switched, she deserves better than that.

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    Re: Radiator fan not turning on

    I always mount a switch. That way I can turn it on sooner then to wait around till 220F -ish. Keeps me cooler in traffic too.

  7. #7
    Right-Wing Nut-Job DavidofColorado's Avatar
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    Re: Radiator fan not turning on

    I say hunt down the thermostat and check it. But it sounds like its bad. Mine fan kicks on at 215 everytime.

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    Re: Radiator fan not turning on

    Not the thermostat... has nothing to do with the fan coming on or not. Before you check for the "switch" disconnect the fan connector and jump it to the battery make sure it comes on, if so then the fan is not bad. Then you can go hunting for the wiring or "switch" issue.
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  9. #9
    Senior Member brennahm's Avatar
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    Re: Radiator fan not turning on

    I'd also check the fan to make sure the motor isn't bad.

    Hate to ask a silly question but are you sure your system is full of water? Absolutely no chance of bubbles or space?

  10. #10
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    When it heats up it blows the reservoir full of bubbles. And I havent done a flush since I've had it. But regardless, that fan should come on. Tomorrow morning I am going to jump the fan and see if it works, then try to find the relay/switch whatever is there....and go from there. UGH, more bike work

  11. #11
    Right-Wing Nut-Job DavidofColorado's Avatar
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    Re: Radiator fan not turning on

    I don't know if its called the thermostat or the thermo coupler but it flicks the switch and turns on the fan. But if you are methodical about it you will work out the problem in no time.

  12. #12

    Re: Radiator fan not turning on

    OK, here we go. Please forgive me if any of this sounds stupid. I am going to try to be thorough, and I don't know what you do or do not know. Plus, I am sick as a dog and only half awake.

    First off, consider that you may have more than one problem. Have you been able to eliminate anything yet?

    Has your fan ever turned on? I don't know how long you've had it. Are you certain that it used to turn on and now doesn't? If you've never heard it before, look at the wires connected to the temp sender. It is a very common mod to install a switch like Motodrew mentioned. Make sure you don't have one. It would just be a toggle switch wired in. This actually happened to me. I had no idea the previous owner had installed one. I couldn't figure out why my fans wouldn't come on. While you are there, make sure the wire is grounded. Test the fan like was said before by connecting it to the battery. This is on the bottom of 8-45.

    Look at 5-2 in your manual. #7 is the thermo switch, and #8 is the temp sender. The cooling system troubleshooting on 8-46/47 will walk you through how to test them.

    Did you get your rad cap pressure tested? If not, do so. Any shop should be able to do it, or maybe even an auto parts store.

    Before you do this next part, decide if you want to check the thermostat. You will need to drain the coolant, so you wanna do it before you reach the next step if you are going to do it. Get the tank and air box and stuff off and get to the carbs. At that point, you just need to undo the rubber boots that connect the carbs to the intakes and disconnect the throttle and choke cables, maybe some hoses, although you may have enough room to reach the thermostat at this point. This is all on 6-1 in the manual. Stuff some clean rags or something into your intakes so nothing can drop in there. Unless you are familiar with this stuff, label the cables and anything else you disconnect so you don't have a problem getting it back together. Then, if you look at 5-8 in your manual you will see getting the thermostat out is pretty easy from this point. Test it in the boiling water with a thermometer.

    Are you still running straight water in there? If so, get some coolant in that sucker. Water doesn't lubricate the internals. Fill it up with 50/50, and make sure you get all the air out. With the rad cap off, lean the bike way over to the left so that the cap side is higher. Replace cap. Run bike. Burp again. And again and again, if needed. Don't burn yourself. If the coolant is boiling, it will expand very rapidly and burst out when you take off the cap. No the water isn't the problem, but air in the system may be part of it and once you know there isn't any, then that can be eliminated.

    Hopefully you won't need to do all of this, but it wouldn't hurt to do it. I would just go through everything and make sure I had a healthy cooling system all the way around. Well, no, that's not true. I would stop as soon as I found something wrong, fix that and go riding. Then I'd be bummed when I was still having problems and had to tear the bike down again, but don't learn from my example.

  13. #13
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Yes since I have had the bike I have seen the fan work. I will be taking the cap off to get pressure tested today. We're going to start there.

    So what is the progression of things that happen?

    1. Thermostat opens cause of heat
    2. Temp sending unit sends info to turn fan on
    3. Fan turns on
    4. Fan stays on till thermostat closes

    I am guessing but is that how it works?

    BHeth, thanks so much AGAIN for your help. I am going to start at the top of your post and keep you posted.

  14. #14
    Right-Wing Nut-Job DavidofColorado's Avatar
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    Re: Radiator fan not turning on

    All of it sounds right until number 4. The fan should stay on as long as the sending unit says its to hot. The thermostat keeps the engine a costant temp so it doesn't freeze. Its not really needed in the summer (or so I've been told). The thermostat will close when the coolant cools down from the water coming from the radiator.

    To test the therostat you can see if the water changes all of a sudden when it first warms up in will flush the system. Its really noticable when you empty out some coolant and then fill back up the radiator it will open up and flush the air out into the rad. If that happens it works.
    The temp sending unit for the fan will kick on when it reaches a set temp and it closes the circut. You can find something screwed into the radiator where water will flow and it has 2 wires coming out of it. If you cross those wires the fan should start.

    That is what I have experience with on my old VF 700. Yours maybe different though and please someone jump in if they know something different.

    ETA: If you need help with it I have tools and time and I live in West Denver. I could help you take a look at it if you get stuck.

  15. #15
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Well I dropped the radiator, and jumpered the fan the battery and she spins up like a top, runs great. Checked to make sure all the connectors are plugged in so now I am going to look in the manual and see if there are ways to check the switches.

  16. #16
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    So the manual says to remove the thermoswitch coupler and jumper the 2 leads together and the fan should come on....It did. Next I had to remove the thermoswitch form the radiator, no problem. Did that, now I need to submerge the thermoswitch in coolant (temperature controlled with a thermometer) and check the continuity as I boil the coolant.

    SHIT....problem, I dont have a thermometer or an ohm meter/continuity checker. So now I am going to walk the neighborhood and see what I can find.

  17. #17
    Right-Wing Nut-Job DavidofColorado's Avatar
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    Re: Radiator fan not turning on

    Actually I can't help there. You could boil it while its hooked up to the bike. Unscrew it and submerge it in water on a hotplate. Or even stick a lighter flame to it for a second or two at a time until it gets warm. It should kick on around 220 for sure.
    I can also make a bong out of a avocado peal and a toilet paper roll.

  18. #18
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Quote Originally Posted by DavidofColorado View Post
    I can also make a bong out of a avocado peal and a toilet paper roll.
    Thats pimp!

  19. #19

    Re: Radiator fan not turning on

    I'd like to see the trick with the avocado. We made stuff out of everything, but never an avocado. Sounds very "California".

    Anyway, do you know anyone who works in a restaurant? They use those pen type thermometers to check food temps and stuff. When I worked in restaurants, these things would be all over the place. Maybe they could "borrow" one for you. That's my best guess unless someone has one you can use. I got one for turkey, but none for antifreeze.

    Maybe you can get a loaner ohm meter from an auto parts store. They loan a lot of shit out, but I don't know if they do stuff like that. I don't have one.

    If you buy them at Walmart you could probably use them and then return them when you're done. They'll take anything back, or so I've heard.

    I dunno, bro. Hopefully someone will come through out here.

  20. #20
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    I just went and bought a meter...pending a return

    The food thermometers I saw only go up to 190 which isnt enough. I am going to do as suggested earlier. Plug it in and heat the bike up, then disconnect and check continuity. What better temp gauge to use then the one on the bike. Gonna try it now.

  21. #21
    Gold Member Bueller's Avatar
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    Re: Radiator fan not turning on

    stick the sender in a pot of boiling water and see if it changes states, the thermometer will tell you at what temp. it happens at, but you can just basic on/off test it without one.


  22. #22
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Well I just ran the bike up to 240, no fan as expected but I could not get the thermoswitch to change state at all checking it with the continuity part of the meter.

    My next question, since this thing has been running hot it has used the coolant/water that was in the reservoir. Should the thermoswitch change state if its not sitting in liquid? Should I let it cool, fill the tanks back up and try it again?

    At this point it appears to be the thermoswitch, but I wonder?

  23. #23
    Senior Member sugarrey's Avatar
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    Re: Radiator fan not turning on

    Now Bueller your saying pull the sender, not the thermoswitch?

  24. #24
    Gold Member Bueller's Avatar
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    Re: Radiator fan not turning on

    Temp sensor


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