Fan Clutch: Description and Operation

Solenoid coupling

General









The engines have a temperature-controlled electromagnetic fan coupling. It is engaged or disengaged by a temperature switch (100°C, G) inserted into the sensor box on the cylinder head. The same function is performed on vehicles with air conditioning system or automatic climate control by a 110°C temperature switch (H). The electromagnetic fan coupling is maintenance-free.

Fan

The fan (75) is mounted on a stud on the coolant pump bearing and is attached by a collar bolt (86).






Design of electromagnetic fan coupling

The solenoid body (68) is attached to the solenoid carrier (68b) by 3 nuts (70). The solenoid carrier is bonded to the coolant pump housing.









The electric cable is connected to the solenoid body by a connector (68a).






The belt pulley is located on the coolant pump shafts ahead of the solenoid body. A steel ring is inserted in the belt pulley which attracts the armature ring on the fan when the fan coupling is engaged (arrow).






The armature ring (77) and the angular-contact roller bearing (76) are installed on or in the fan, respectively.

Function






The fan is engaged only when the ignition is switched on and at a coolant temperature above 98 - 102°C.
A constant positive exists at the solenoid body (68).
Below a coolant temperature of 98 - 102°C, the fan is switched off and only rotates as a result of the airstream or as a result of the bearing friction.
Minus is engaged at a coolant temperature of not more than 102°C through the temperature switch (G or H) at the sensor box.
The armature (76) is attracted by the solenoid body (68) and presses against the end face of the belt pulley.
The fan is now rigidly connected to the belt pulley and rotates in line with the coolant pump speed.
If the coolant temperature drops below 93 - 98°C, the temperature switch opens and the armature (76) is lifted off the belt pulley by the leaf springs.
On vehicles fitted with air conditioning or automatic climate control, the fan and the electric auxiliary fan are engaged by a double-contact relay which is activated by the triple temperature switch (H).