Radiator fan

[Oceandiver11764]

Help?

The red light has been coming on sporadically for a while now.  Today it became solid red (about 85 degrees outside).  
I got home and left the bike running to check the fan...no fan.
I checked the fuse, fuse OK.  I pulled the wire off the switch in the lower left corner of the radiator and the fan came on.
Seems like I changed this switch once before, but my memory isn't what it used to be.
Does it sound like this switch in the radiator is bad?

Update:  I did some rooting around and found I have that switch, a new one still in the parts bag.  I replaced it, and added some coolant for what I lost doing it.  Went for about a 2 mile ride, red light went out but the fan did not come on, from what I could tell at traffic lights.  When I got to the garage I let it idle, and the little red light began to flicker again, went out, and stayed out...but again the fan never came on.  If the fan is working, and the switch is new, what else can I check ?  Help ?

I am just crazy guessing, but could there be air trapped in the radiator causing the sensor not to sense?

I put teflon tape on the sensor threads, could that be stopping the sensor from grounding?

[WintrSol]

"I put teflon tape on the sensor threads, could that be stopping the sensor from grounding?"

Got a Volt-Ohmmeter? Everything off, set the meter to lowest Ohms scale, and measure from the sensor housing to the engine block. Your answer should be there.

[Oceandiver11764]

"I put teflon tape on the sensor threads, could that be stopping the sensor from grounding?"

Got a Volt-Ohmmeter? Everything off, set the meter to lowest Ohms scale, and measure from the sensor housing to the engine block. Your answer should be there.

Thank you for that !  I got a reading from the sensor housing to the block, but it is sort of weak and definitely sporadic.  I cleaned off the teflon tape and it definitley made a difference (see below).

I took the sensor that I replaced yesterday, which I think is pretty new, put heat to it and it closed like it should, on the "test stand".  I cleaned off any teflon tape I could find or see, and put it back in the bike.  Same problem, fan wouldn't run.  I shut off the bike and let it sit for a few minutes while I wondered what to try next, I put a jumper between the block and the sensor housing and still, same problem.  Shut off the bike and restarted, all of sudden the freakin' fan is coming on, and cycling.  Took it for a ride around the block and parked in the garage again, rev'd it up, just as the red light blinked, the fan came on like it should.

Again, the fan works when I jump it's wire to ground.  
Could it be that some of these sensors just don't work right?  
Here is one on ebay, they seem to be around.  Maybe I should try it?
https://www.ebay.com/itm/175828391450

[WintrSol]

Just to be clear, the fan motor switch is not connected in any way to the red overheat light; it should actually turn the fan on before the light does. The fan switch should turn on at 208-218F. while the thermostatic switch (which turns the light on) at 234-244F. The fan switch is mounted to the radiator lower left corner. the other to the thermostat housing at the top of the engine.

So, which one are you changing out?

It is odd that the temperature range is so different, when the parts listing at Partzilla shows the same part number Also, CyclePartsNation shows different part numbers, which is probably correct.
37760-MT2-003 fan
36151-MT8-003 light

[Oceandiver11764]

Just to be clear, the fan motor switch is not connected in any way to the red overheat light; it should actually turn the fan on before the light does. The fan switch should turn on at 208-218F. while the thermostatic switch (which turns the light on) at 234-244F. The fan switch is mounted to the radiator lower left corner. the other to the thermostat housing at the top of the engine.

So, which one are you changing out?

It is odd that the temperature range is so different, when the parts listing at Partzilla shows the same part number Also, CyclePartsNation shows different part numbers, which is probably correct.
37760-MT2-003 fan
36151-MT8-003 light

I am changing the radiator fan switch, lower left corner.  When the light is on, I don't feel an excessive amount of heat radiating from the bike, made me think it could be the light switch.  But for sure the fan is not coming on.

[WintrSol]

A PO of my bike added a water temp gauge and oil pressure gauge, both very handy, so I know exactly what temperature my fan comes on. Never seen the temp line on while engine was running. Also, my fan doesn't run very often, unless I'm getting off a high-speed run onto a slow side road.

Make sure your cooling system has no air in it; the coolant return bottle should rise and fall, and, when removing the radiator cap (cold), the radiator should be full to the top. An air bubble at the thermostat can cause the light to come on because coolant doesn't surround the switch. If necessary, when refilling the coolant, I have the front tire up on a board to lift the front before the first warmup, then check for air after it cools.

[Oceandiver11764]

A PO of my bike added a water temp gauge and oil pressure gauge, both very handy, so I know exactly what temperature my fan comes on. Never seen the temp line on while engine was running. Also, my fan doesn't run very often, unless I'm getting off a high-speed run onto a slow side road.

Make sure your cooling system has no air in it; the coolant return bottle should rise and fall, and, when removing the radiator cap (cold), the radiator should be full to the top. An air bubble at the thermostat can cause the light to come on because coolant doesn't surround the switch. If necessary, when refilling the coolant, I have the front tire up on a board to lift the front before the first warmup, then check for air after it cools.

Thanks for the tips.  I will engage them in the next day or so, to make sure of things.  I just went for another test ride, came back, and the fan kicked on in my garage, no red light.  Only things I changed were the switch itself, and after seeing the ohm meter, removing all traces of teflon (and of course screwing the switch in/out several times during the process contributed to cleaning up the threads). 

Last question and I'll leave you alone.  I read in several posts (some were for cars) that the radiator ground wire can mess up, causing the same problem.  I was thinking of running a new ground wire from the radiator to the frame...just to make sure I have a good ground on the radiator.  What do you think of this idea?

[WintrSol]

Extra grounds never hurt, IMO, as long as you have good, clean attachments.

[98valk]

Extra grounds never hurt, IMO, as long as you have good, clean attachments.

sometimes double grounds make things not to work. like auxiliary lights and horns.

[WintrSol]

Extra grounds never hurt, IMO, as long as you have good, clean attachments.

sometimes double grounds make things not to work. like auxiliary lights and horns.

Depends on where, ans what the ground supports. The only thing grounded to the radiator is the fan bypass filter, on the Interstate, and a better ground would only help. But, yes, electronics can suffer from a ground loop with multi-point grounds. Lights and horns, usually not.

[Jims99]

I know certain years have the red light is controlled by an ohms style switch. Over time they can give false readings. I have a 99 that does it at the weirdest times, not hot and not cool. There is a thread somewhere on here about using the newer style switch and how to bypass the control box part. Ive never done it because it doesn’t bother me when the light comes on. Goes off within a few seconds and never feel any extra heat. My fan comes on sitting in traffic sometimes but the light usually flickers or stays on a bit while cruising.

[Oceandiver11764]

I ran the ground from under the screw that holds the radiator side cover in place, to the bolt holding the highway bar in place.  Wire brushed both areas first, clean metal to metal connections.  Very short and unobtrusive.  For my purposes it worked great.  Now I have absolutely no resistance between the radiator and the frame of the bike.
Took a 60 mile test ride yesterday, almost 90 outside, fan came on as expected at long traffic lights, no red overheat light coming on at all.

[HayHauler]

Great!  Thanks for letting us know what the solution was.

Hay 
Jimmyt