Emergency mode of 2-battery on-board electrical system, function - GF54.10-P-1103SX
MODEL 216.3, 221.0 /1 up to Model Year 8
Starting vehicle with discharged battery (G1)
If the voltage of the on-board electrical system battery has dropped below 8 V, it is only possible to open the vehicle mechanically using the emergency key. When the transmitter key (A8/1) is inserted into the EIS [EZS] control unit (N73), a microswitch in the EIS [EZS] control unit is closed. The vehicle power supply control unit (N82/1) energizes the battery coupling relay (F32k1) and couples the starter battery (G1/4) with the on-board electrical system battery for 5 min. After circuit 15 is switched on, the coupled on-board electrical system is available for 30 s.
Alternator (G2) defective
If an alternator fault is detected when the engine is running (also e.g. cracked V-belt or open circuit), the on-board electrical system is supplied with power from the on-board electrical system battery until this battery is discharged and the engine stops running as a result. When the engine is started again, the "on-board electrical system battery discharged" state is detected.
The battery coupling relay is energized and power is then supplied from the starter battery.
Open circuit on on-board electrical network line
If the on-board electrical network line has an open circuit, e.g. caused by a triggered on-board electrical network line pyrofuse (N82/1f1), the effect is initially the same as for a defective alternator.
The on-board electrical system is supplied with power until the onboard electrical system battery is discharged and the engine stops running as a result. The engine can, however, no longer be started in this case because the supply of power from the starter battery is not possible owing to the open circuit.
Function of on-board electrical system emergency mode
If one of the above-mentioned cases occurs, the vehicle power supply control unit outputs the "on-board electrical system emergency mode" signal on the chassis CAN.
This activates the following functions:
- Minimum voltage for consumer shutoff is increased from 12.2 V to 12.8 V
- Idle speed increase via the CDI control unit (N3/9) on diesel engines or via the ME-SFI [ME] control unit (N3/10) on gasoline engines
- Deactivation of excitation current limitation by the CDI control unit or the ME-SFI [ME] control unit (nominal voltage of alternator 14.2 V)
- Requests for consumer shutoff with the engine running are output with a shorter delay (0.1 s instead of 1 s):
Shutoff sequence (depends on equipment installed)
- Stage 3 (passenger-side) of PTC heater booster (R22/3) heating element
- Stage 3 (driver-side) of PTC heater booster heating element
- Stage 2 (passenger-side) of PTC heater booster heating element
- Stage 2 (driver-side) of PTC heater booster heating element
- Stage 1 (passenger-side) of PTC heater booster heating element
- Stage 1 (driver-side) of PTC heater booster heating element
- Rear blower motor (M2/1) is reduced to 50 %
- Blower motor (A32m1) is reduced to 50 %
- Omission of air-conditioning request for engine and air-conditioning electric suction fan with integrated control (M4/7)
- Trailer hitch socket (13-pin) (X58), circuit 30
- Front cigar lighter with ashtray illumination (R3), power outlets etc.
- Seat heater stage 3
- Rear window defroster
- Wiper park position heater
- Seat heater stage 2
- Seat heater stage 1
- Heated steering wheel
- Heated windshield
- Mirror heater
After the shutoff requests have been output, the following short-time consumers are also switched off (depends on equipment installed):
- Stationary heater (STH)
- Remote trunk closing (RTC [HDFS])
- AIRmatic compressor unit (A9/1)
- Multicontour seat (MKS) or dynamic seat (FDS)
To ensure that the battery has time to recover, the functions of the on-board electrical system emergency mode remain active for 30 min.
If the alternator load factor drops below 90 % and the on-board power supply voltage exceeds 12.8 V, the consumers are activated again in stages.
Engine OFF
If the engine is OFF, the operating condition "engine OFF" still applies to the consumer shutoff, even if the ON time for the on-board electrical system emergency mode of 30 min has not yet expired:
Shutoff sequence (depends on equipment installed)
- Wiper rest heater
- Seat ventilation
- Seat heater stage 3
- Rear backrest refrigerator box (A39/1)
- Rear blower motor is reduced to 50 %
- Blower motor is reduced to 50 %
- Electric suction fan for engine and air-conditioning system is reduced to 50 %
- Seat heater stage 2
- Seat heater stage 1
- Heated rear window
- Heated steering wheel
- COMAND controller unit (A40/3)
- Trailer hitch socket (13-pin)
Luggage compartment socket (X58/12), front cigar lighter with
- Heated rear window
- Heated steering wheel
- COMAND controller unit (A40/3)
- ashtray illumination, rear cigar lighter (R3/1)
- Roof sign, printer, card reader
- Interior illumination
| ME-SFI control unit, location/task/design/function | N3/10 Model 221 with engine 275.953/982 |
GF07.61-P-5000M |
| ME-SFI [ME] control unit, component description | N3/10 Model 221 with engine 272.965, 273.961 Model 216 with engine 273.961 |
GF07.61-P-6000V |
| Electronic ignition/starter switch control unit (EIS) component description | N73 | GF80.57-P-6000SX |
| Vehicle power supply control unit, component description | N82/1 | GF54.21-P-4126SX |
| Central gateway control unit, component description | N93 | GF54.21-P-4170SX |