radiator fans cycling ?

roadrider

roadrider

Joined
Aug 16, 2008
Messages
72
Location
goldendale wa.
07 st 1300 45,000 miles, coolant changed/radiator cleaned at 36,000 miles. 3 bars on dash after warm and stays there on highway or in town. when I slow stop n go in town even at 60 degrees the fans will cycle on/off. is this normal or ? reply makntraxs@aol.com greg
 
Yup, when you aren't moving .. there's no air flow so the fans have to do something to cool off the water that's being heated by the engine.
 
Even in the cold north, less than 60F, while driving slow into my neighborhood, my fans are on before I get to my Garage. Sounds normal to me as well.
 
I wondered about that too. This is my first water cooled bike and the first time I heard the fan turn on it caught me off guard.
 
These work just as a cage, fluid temp gets up, sensor in the rad signals a relay to supply power to the fans since there isn't enough cooler air through the fins. You just don't hear the ones in a cage as there is so much more noise.
 
I often ride with denim bike shorts (keeps the sunburn off the knees),,, in the summer season. So I can feel the fans come on,, both with warm air across the shins,,, and even warming up my Corbin seat pan. It is quite bearable,,, and I should mention that for the importance of good footware/grip,,, I do wear 6" motorcycle boots. In the spring and fall,,, having the fans come on is actually pretty comfortable. Next time I dig into my tupperware,, I will install an amber led on the fan circuit,,, so that there is a visual indicator when they are operating. Simple and cheap,,, and it is mostly because I am curious about how the fan cycles at road speeds,,, when there is such a volume of air moving through the bike, that you can not feel the fans come on,,, and/or hear them above the engine/wind/tire noise. My bike never goes above 3 bars, and that means that the fan sensor must be set to come on between 3 and 4 bars on the temperature indicator,,, Cat'
 
Catmandu2 said:
,, and it is mostly because I am curious about how the fan cycles at road speeds,,, when there is such a volume of air moving through the bike, that you can not feel the fans come on
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Minimal, depending on the ambient air temp. As long as there is enough air through that is cooler than the rad sensor, no need for the fans to come on. If working the bike engine hard in the heat, like pulling a trailer up hill, yes, fans would come on.
 
Had a problem with my fans coming on frequently and ended up finding that the radiator was indeed plugged......on the outside. Pulled it off, soaked it in warm water and cleaned the fins with a small brush. high mileage radiators plug up on the outside too. Bugs will do that on cars too.
 
As long as there is enough air through that is cooler than the rad sensor, no need for the fans to come on.If working the bike engine hard in the heat, like pulling a trailer up hill, yes, fans would come on.
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At lower speeds I agree. I don't see that being the case at speed however. At 50 MPH I would think that the air flow through the radiator far exceeds what the fans can pull through it. The air flow through the radiator is determined by and remains constant with the road speed, not the load on the engine. If the fans are coming on at higher speeds, regardless of load, I would take that as an indication that there is a cooling system deficiency somewhere.

Now I am curious. I wear ear plugs all the time. At anything above 30 or 40 MPH I can't tell if/when the fans operate on my ST1300. Does anyone know if they do at higher speeds? Say above 45 or 50 MPH?
 
The fans are controlled by the temp switch. They come on when the switch says to come on. Yes when the fans come on and go off frequently you have a cooling problem, it just isn't internal when the outside is plugged. I found mine by shining a flashlight through the side panel, and verified by running the fan and sticking my hand in front. It was only moving air at a section that was cleansed by the fan. The fender is short enough to put a lot of road dirt into it
 
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