What Causes the Fan of a Water-Cooled Motorcycle Not to Spin When the Temperature is High?
3 Answers
Water-Cooled Motorcycle Temperature High Fan Not Spinning Reasons Are as Follows: Thermostat Switch Issue: Problems with the thermostat switch can affect the operation of the motorcycle's radiator fan, so it's important to inspect and replace any damaged thermostat switches. Fan Malfunction: If the fan is faulty, it should be replaced promptly to maintain proper cooling function. Relay Failure: A faulty relay can also prevent the radiator fan from operating normally. Inspection Steps: If the electric fan is not working, first check if the connector has poor contact, inspect the power supply and grounding of the electric fan, check if the fan is stuck, and examine whether the fan motor is burnt out, etc.
Buddy, I've been repairing motorcycles for 20 years and seen too many such issues. There's an 80% chance it's a faulty temperature switch - if it can't sense rising coolant temperature, it won't power the fan. The second possibility is a seized or burnt-out fan motor. Try connecting the fan directly to the battery to check if it spins. Also thoroughly inspect for oxidized or loose wiring harness connectors - last time I fixed a Ducati, the plug was clogged with mud. And don't forget to check that 15A purple fuse in the fuse box. I recommend first cleaning dust accumulation from the radiator fins - sometimes simple cleaning solves overheating. If the fan makes grinding noises, replace the bearings immediately before the motor smokes.
I rode my water-cooled bike through the Sichuan-Tibet line, and the fan failure was a real nightmare. Common issues include: a faulty water temperature sensor causing the ECU to misjudge the temperature; burnt relay contacts preventing electrical flow; and wiring melting due to modified exhaust pipes—a frequent occurrence. I remember that time in Litang when I had to use a paperclip to short-circuit the thermostat switch to force the fan to run. Now, during every maintenance check, I ask the mechanic to measure the fan's resistance, which should normally be 3-5 ohms. A word of advice: keep an OBD scanner handy—it's dangerous if the dashboard doesn’t alert you when the water temperature exceeds 95°C. Also, don’t wire auxiliary lights haphazardly. Last week, someone in our riding group fried their ECU fan control module due to improper wiring.
