Many motorcycle manufacturers have replaced their traditional air-cooled engines with water-cooled systems, which are similar to those used in automobiles. Water-cooled engines have the advantage of running at a sustain regulated temperature, which offers better performance and longer engine life. The drawback to water-cooled systems is that the thermostat, thermostat fan switch and the fan itself must all work together to keep the system from overheating. If the fan stops working, you can test the motorcycle fan switch and the fan simultaneously by bypassing the fan switch and hot-wiring the fan.
Disconnect the positive and negative wires that lead into the thermostat fan switch.
Disconnect the positive and negative wires that lead from the fan switch to the fan.
Connect the positive wire, that led to the fan switch, directly to the positive wire leading to the fan. Connect the negative wire, that led to the fan switch, to the negative wire leading to the fan. This will bypass the fan switch, essentially hot-wiring the fan, to determine if the fan itself is working.
Turn on the ignition. If the fan activates, the switch is faulty.