The DDE control unit activates the electric fan by means of a square-wave signal with duty factors (= variable pulse width) between 5 and 90 % and thus controls variable speeds of the electric fan. The electric fan features its own positive and ground supply.
The activation function is monitored for short-circuit and open circuit but not the fan motor itself. Fault code 0480 "Electric fan" is stored if a defect occurs.
Consequence: Engine temperature increases
The fault code entry "electric fan, short to ground" may be caused by a mechanically blocked fan motor (in winter by frozen condensation water).
Note: As from 03/00 mechanical blocking of the fan will be detected as such and the type of fault “Electric fan mechancially blocked” will be stored.