application.
On cars with automatic transmissions,
the main fan is electric and mounted on
the bumper side of the radiator. The fan
is controlled by the DME control module
via the output final stage. Additionally a
belt-driven fan via a viscous fluid
coupling (clutch) is attached to the front
of the coolant pump. The fan clutch
controls the speed of the fan based on
engine compartment temperature.
On cars with manual transmissions, a
single multi-speed electric cooling fan is
used. The fan is mounted on the engine
side of the radiator and controlled by the
DME control module via the output final
stage.
On both configurations, the output final
stage is mounted on the fan housing,
next to the fan motor. The fan is
operated using a pulse width modulated
(PWM) signal and is protected by a
50-amp fuse. Electric fan activation is
based on the following inputs to the
ECM:
Radiator outlet temperature
Catalyst temperature (calculated
temperature)
Vehicle speed
Battery voltage
A/C pressure (calculated pressure)
When the vehicle is first started, The
ECM activates the electric fan briefly at
20% of its maximum speed, then
switches off. This is for diagnostic
monitoring. The voltage generated by
the fan when it slows down (acting as a
generator) must match the stored `rpm'
Radiator and Cooling System
http://ebahn.bentleypublishers.com/BMW/3/E46/Repair%20Manuals/1...
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Summary of Contents for 1999-2005 M3
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