Mercedes-Benz 212 Sedan E-Class Service Manual page 78

Consumer shutoff
In order to prevent complete discharge of the on-
board electrical system battery in all driving cycles,
the on-board electrical system voltage is continuously
monitored by the battery sensor and evaluated by the
rear SAM control unit. The operating rate of the alter-
nator is also monitored.
In phases where the alternator can no longer supply
the demands for electrical power, the on-board elec-
trical system management system employs a dynamic
load management function to reduce the load on the
electrical system by successively shutting down
convenience functions (consumer shutoff).
This guarantees a positive charge balance and
ensures that starting ability is preserved. As soon as
the power supply is sufficient, the consumer shutoff is
revoked accordingly.
Main components of on-board electrical system, shown on the E 250 CDI
B95 Battery sensor
F32 Front prefuse box
G1 On-board electrical system battery
– This printout will not be recorded by the update service. Status: 01 / 2009 –
On-board electrical system
Dynamic idle speed increase
The dynamic rpm increase is intended to adjust the
idle speed of the engine so that no power is drawn
from the on-board electrical system battery while
idling. Accordingly, when consumer load is high, a high
idle speed is set. In contrast to the previous rpm
increase function, which takes effect when the voltage
drops below a given limit or when a certain consumer
shutoff stage is reached, the dynamic idle speed
control acts preventively. Therefore it does not react
to a lack of electrical energy, but determines in
advance the necessary idle speed for the current load.
The required idle speed increase is computed via the
on-board electrical system control in the rear SAM
control unit and forwarded to the CDI or ME-SFI
control unit. This calculates the idle speed that is actu-
ally required, taking into account various engine char-
acteristics.
G2 Alternator
N3 / 9 CDI control unit
N10 / 2 Rear SAM control unit with fuse and relay
module
Introduction of the New E-Class, Model Series 212 Sedan
P54.10-3112-00
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