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:
Quote from: WintrSol on July 19, 2025, 02:14:47 PM
"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:
Quote from: WintrSol on July 20, 2025, 08:24:25 AM
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.
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