Mercedes-Benz W201 radiator fan not spinning
W201 radiator fan does not spin even though the engine overheats – what controls it?
On the petrol model the fan is controlled by an electric magnetic clutch. The clutch is switched on by a two-pin temperature sensor at the front of the cylinder head, usually at around 100 degrees. If the sensor is broken, the fan does not start. The thermostat's operation affects the temperature at which the fan kicks in.
How can I test the fan?
Let the engine run, unplug the sensor connector and join the two pins of the connector with a wire. If the fan starts to spin, the fault is in the sensor. If it does not, the fault is in the relay, wiring, magnetic clutch or the fan itself.
What other faults should I check?
Check the fuse, relay and wiring. The magnetic clutch ground wire can come off its connector on top of the water pump, and the wire can break. The fan connectors can also oxidise, in which case cleaning and reconnecting helps. If the fan spins but makes noise, the cause is often a bearing.