Alternator Control, Basic Function - GF15.40-S-1058A

Engine All (Light transporter) 

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 signal acquisition and actuation module 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 200 in model 420	PE07.10-S-2504VRA
		Engine 608 in model 420	PE07.10-S-2504VRB
	Control units
	Combustion engine control unit, basic function		GF07.08-S-9890A