The speed switching is performed by connecting additional resistors of different values. The resistors are connected to the break of the positive power supply wire of the fan motor. The connection to ground is constant.
ATTENTION: The fan sucks outside air into the water drainage channel. There is a grate on the inlet pipe. Despite this, small leaves may get into the fan and make an annoying noise when it is running. In this case, you need to disconnect the plastic bracket on the grate, remove the grate and try to remove foreign objects from above.
If the fan does not work in any switch position, check the fuse first.
If, despite a working fuse, the windscreen wiper also does not work, the cause may be in the contact unloader relay.
Clear access to the fan motor.
Disconnect the plug on the fan motor, connect the two auxiliary wires to the contacts that are now visible.
[The text of the article was taken from the website: mitsubishiman]
If the fan motor is good it should run at full speed. If not, replace it.
If the fan only runs at full speed, the overheat fuse on the resistor board may be blown.