On-board electrical system power supply, function - GF15.40-P-0001MCU

ENGINE 132.9 in MODEL 451.3 /4 

General 

When the engine is running, the alternator supplies the on-board electrical system with electrical energy and charges the battery. For this purpose, the alternator generates three-phase current which is rectified.

Function 

The power supply for the on-board electrical system is monitored and regulated by the ME-SFI [ME] control unit.

For circuit 15 On voltage is applied to connector D+ of the alternator.

However as long as no charging voltage is recognized by the ME-SFI [ME] control unit, it requests switching on of the charge control and alternator warning lamp via the CAN.

After starting the engine, the alternator produces the preexcitation current itself. The alternator delivers current via connector B+ to the battery and to the on-board electrical system. The alternator voltage lies slightly under the gassing voltage of the battery which achieves adequate charging and prevents damage to the battery through overcharging.

The ME-SFI [ME] control unit then switches off the request to the charge control and warning lamp.

If the on-board power supply voltage is less than 11.5 V for longer than 3 minutes, a signal is sent to the instrument cluster via the CAN to switch on the charge control and warning lamp.

Control 

The alternator is regulated by the integral electronics depending on the:

• RPM
• Vehicle power supply voltage
• Request from the ME-SFI [ME] control unit
• Ambient temperature

The status of the momentary operating rate of the alternator is monitored by the ME-SFI [ME] control unit. The regulating voltage in neutral is 13.5 V and for a maximum engine speed about 14.5 V.

The alternator is connected directly with the ME-SFI [ME] control unit.

The following functions are implemented:

• Preexcitation
• Feedback of the alternator load
• Voltage demand by the ME-SFI [ME] control unit

	On-board electrical system power supply Location of components		GF15.40-P-0001-02MCU
	Wiring diagram for starter, alternator		PE15.00-P-2000MCU
	Component description for the instrument cluster	A1	GF54.30-P-6000MCU
	Component description for the alternator	G2	GF15.40-P-2000MCU
	Component description for the ME-SFI [ME] control unit	N3/10	GF07.61-P-6000MCU