ME alternator interface function - GF07.61-P-3003V

ENGINE 272.942 in MODEL 171 

ENGINE 272.963 in MODEL 171 

Messages between the engine control unit and the alternator are exchanged via the alternator interface. The tasks are:

• Switch on and regulate alternator following the engine start according to the performance maps stored in the engine control unit. To do this, the control voltage is preset by the engine control unit.
• Adapts the control voltage with a delay in the event of frequent load changes at the alternator to stabilize idling.
• Protects alternator against overheating.
• Generates circuit 61 (information "alternator is turning").
• Detects fault and actuates charge indicator/multifunction display.

The engine control unit actuates the control response of the alternator via the alternator interface, in order e.g. to decrease the charging voltage in idle when battery is sufficiently charged. Less fuel is injected due to the reduced engine load. Fuel consumption is reduced and the exhaust characteristic is further optimized.

For alternators with an alternator interface, the line with circuit 61 (information "alternator is turning") is no longer required. From the information which the engine control unit receives via the alternator interface, the terminal 61 in the engine control unit is simulated and is indicated via a downstream of ground shifting output stage e.g. for the instrument cluster.

The alternator constantly performs self-diagnosis and sends the results when requested to the engine control unit. The engine control unit compares them with other signals (e.g. engine speed, battery voltage and time after engine start) and detects the following faults:

• Electrical and mechanical faults at alternator (regulator or diodes defective, stator interruption or short circuit, exciter interruption, regulation voltage and charging current are not achieved, regulation voltage too high, cracked or loose poly-V-belt).
• Short circuit or open circuit at output terminal 61 of engine control unit.
• Line of alternator interface between engine control unit and alternator interrupted, or defective interface driver in engine control unit. In the event of such an error, a control voltage from 13.45 V to 14.15 V is preset.

The upper limit value of the regulation voltage can be up to 15 V. If the battery is full or discharged, the regulation voltage be reduced do to the battery voltage.

For alternator test and test prerequisites see STAR DIAGNOSIS (menu item "Actuations" or "List of tests performed").