Speed switching is carried out by connecting additional resistances of different sizes. The resistances are included in the break in the positive wire of the fan motor power supply. Ground connection is permanent.
WARNING: The fan draws outside air into the drainage channel. There is a grate on the inlet pipe. Despite this, small leaves can get into the fan and produce annoying noise during its operation. In this case, you need to disconnect the plastic bracket on the grill, remove the grill and try to remove foreign objects from above.
If the fan does not work in any position of the switch, check the fuse first.
If, despite a good fuse, the glass cleaner also does not work, the cause may be in the contact relief relay.
Free access to the fan motor.
Disconnect the plug on the fan motor, connect the two auxiliary wires to the contacts now shown.
If the fan motor is OK, it should run at full speed. If not, replace it.
If the fan only runs at full speed, the overheat fuse on the resistance board may be blown.