The fans should come on automatically when the temp reaches 100 degrees and go off again when it drops below 94 or 95. There is a relay located under the seat which controls this. Don't know where the temp sensor is though, sorry. I have actually fitted a flick switch to turn the fans on manually as I feel that 100 degrees is too late to be bringing the fans on. As i live in a hot country, I turn the fans on when I am in town by wiring direct from a switch to the relay an in effect making the contact. You could test the relay by simply bridging between the terminals to see if the fans come on. If they work then the problem may be with the sensor if not then the relay will be at fault.
The relay is small and black with a white/clear connector coming out of the main loom. It is located behind the battery and directly under the front seat release mechanism (not key on the side but where the seat clips into). The white/clear connector has four wires - Red, Brown with Green stripe, Red with White stripe and Grey. The Grey wire is much smaller and this is the one you want. If you touch a wire between where the small grey wire is connected and the battery NEGATIVE terminal (ie earthing the connection) with the ignition on the fans should come on. This is a volt-free contact so no chance of shock! As I said above, if the fans run then the problem may well be with the temp sensor.
Also setting at what temp the fan comes on is not adjustable without adding more complicated electronics.
The link I have included below is what I used to install my manual running switch which has some pictures and may be of use to you. It is for an older model FZ1 but the principle is the same.
http://www.angelfire.com/ia/z/FZ1fanswitch.htmHope this is of use and good luck.