Checking the fan (Audi 100 C4)

The fan motor operates at four speeds, set using a regulator on the front panel. Speed is changed by connecting resistors of different sizes. The resistors are connected to the fan motor via the "ground" wire, and the positive voltage wire remains constant, i.e. only the contact with the ground is "improved" or "worsened".

If the fan does not work in any switch position, the corresponding fuse should be checked first.

If, despite a working fuse, the windshield wiper does not work, then the fault is in the unloading relay of contact "X".

Check the fan motor: remove the motor plug and connect the auxiliary wires to the released contacts and then: from the battery "plus" to the contact of the black/blue wire, from the "minus" to the contact of the red/brown wire.

If the motor is in good condition, it should rotate at maximum speed. If it does not, replace the motor.

If the engine does not work at all speeds, then the additional resistors may be faulty.

Remove the resistors and visually inspect them. If one of the resistors burns out, replace the entire unit.

If the resistors are OK, all that remains is to check the wiring or switches - replace the faulty ones.

(Text provided by the online resource AUDIMANUAL.RU)