Overview
This document contains information on:
General
Function requirements
Function
General
To optimally control the charging voltage of the alternator, the alternator and the combustion engine control unit exchange data via the alternator control function. The alternator control function makes the exchanged data plausible and corrects it depending on the vehicle’s operating state. In addition, the alternator control function records mechanical or electrical faults in the alternator.
Function requirements
Engine management ON (circuit 87M)
Engine in operation
Function
Alternator control function
The alternator control function requests the optimized charging voltage from the alternator. The optimized charging voltage is calculated from the following information:
Specified voltage of the alternator management
Corrections by output management
In order to calculate the optimized charging voltage for the alternator, the following processes take place:
Reading out the operating rate of the alternator
In order to control the power output of the alternator, the combustion engine control unit assesses the operating rate of the alternator. To this end, it uses the data transmitted by the alternator.
Calculating the specified voltage of the alternator
In order to determine the specified voltage of the alternator, the body/drivetrain central control unit uses the operating rate of the alternator. This involves the alternator control function.
Optimizing the specified voltage of the alternator
In order to record the on-board electrical system voltage, the following information is read in and compared:
The calculated specified voltage of the alternator
The actual value of the alternator voltage
In order to compensate for fluctuations in the on-board electrical system voltage in certain vehicle operating states, the output management optimizes the specified voltage at engine start, for example. This results in the optimized charging voltage.
Alternator self-diagnosis
The alternator performs self-diagnosis continuously. On request, it provides its status as a signal.
The alternator control function detects the following electrical or mechanical faults:
Line of the alternator control function has an open circuit
Control or diodes defective
Interruption or short circuit in the stator
Excitation interruption
Charging voltage too low or too high
Cracked poly-V-belt
Poly-V belt tension too low or too high
Function schematics | |||
Function schematic for alternator interface | Engine 260, 282, 608 in model 118, 177, 247Engine 264 in model 167 | ||
Engine 176, 177 in model 167 | |||
Engine 139 in model 118, 177 | |||
Engine 254, 256, 264 in model 213 as of model year 2021Engine 256 in model 238 as of model year 2021Engine 654 in model 118, 167, 177, 247Engine 654 in model 213, 238, 257 as of model year 2021Engine 656 in model 167, 223 | |||
Engine 176, 256 in model 223 | |||
Engine 279 in model 223 | |||
Control units | |||
Combustion engine control unit, basic function | Engine all (CAR) |