My cooling fan wont turn on. Could it not work if the radiator wasn't completely full?

 

i doubt that the fan wouldn't work if the radiator wasn't full, sounds like an electrical situation to me. there is a clip on the left side of the fan that kept coming undone on mine and every time it disconnected the fan would turn off. you might want to start there. if that isn't it you may have a short somewhere, cross your fingers for the clip just popping loose.

 

On the back left side of the radiator is a thermo switch that controls the fan motor. With the key in the on position, take the wire off the thermo switch and short it to ground. The fan should come on immediately. If it doesn't, check to see if you've got 12v at that wire when it's not attached to anything. 12v, bad fan, no 12v, then maybe bad fuse or wiring. As for being low on coolant, yes it could cause it not to come on. Water is like the 2nd best conductor of heat. When you have enough coolant in the engine and radiator, it circulates bringing hot water out of the engine, which heats the radiator. That in turn naturally heats the thermo switch and turns on the cooling fan. If you have insufficient coolant in the bike to circulate, then the radiator has a lot of air in it, which doesnt' conduct heat very well. The thermo switch may never get hot enough to turn the fan on. Meanwhile, your engine is overheating. Not a good thing. Definately make sure you have enough coolant and that it's circulating.

 

there is a couple of things it could be. i've had the luxury of tearing my bike apart a fews times for cooling issues. first, check the fuse. i've had that happen, could be simple as that. i would also check your coolant level. the fan switch is mounted on the lower left side of the radiator from the rear. it detects the water temp and turns on the fan when you get to i think 219, but anyway, if the fluid is too low it can't detect the temp. make sure you are full. beyond that the next two areas could either be a bad fan switch or possibly a bad fan motor. you'll need a multi-meter to check those. you'll have to check for proper voltage and continuity. i can look up values in my service manual if you need them. let me know. good luck.