Consumer shutoff function - GF54.10-P-2002CW

MODEL 204.0/2 up to Model Year 2008 

Consumer shutoff in general 

In order to ensure that the on-board electrical system battery (G1) is not discharged in any of the driving cycles, the on-board power supply voltage is continuously monitored by the battery sensor (B95) and evaluated by the rear SAM control unit with fuse and relay module (N10/2). The operating rate of the alternator (G2) continues to be monitored. If necessary, the rear SAM control unit send the consumer shutoff requests to the interior CAN.

Each of the control units then switches the consumers off or reduces their respective output. The consumer shutoff voltage threshold is temperature specific. This means that the lower the battery temperature, the higher the on-board power supply voltage at which the consumer shutoff is activated.

The consumer shutoff function is made up of the following subfunctions: 

• Consumer shutoff
• Activation of consumers when engine is off
• Activation of consumers when engine is running

Consumer shutoff function sequence 

Function requirement 

• Temperature-specific lower limit reached
  • With engine running (circuit 61 ON):

    (e.g. U < 12.4 V with T = 20 °C and t > 2 s)

  • With engine off:

    U ≤ 11.8 V

Consumer shutoff function sequence 

When the engine is running the first consumer is switched off after t = 20 s. Under identical switch-off conditions, one consumer is additionally switched off every second.

When the engine is switched off, a change from circuit 15C to circuit 15R ON will activate the consumer shutoff after a waiting time in each case of t = 30 s.

When the engine is switched off, the switch-off stage is adopted that was active when the engine was running.

Consumer shutoff for PRE-SAFE actuation (with code (299) PRE-SAFE):

The left front reversible emergency tensioning retractor (A76) and right front reversible emergency tensioning retractor (A76/1) both have extremely high startup and function currents. This is why several high-output consumers have to be switched off for approx. t = 2 s as quickly as possible, to relieve the load on the on-board electrical system when a reversible emergency tensioning retractor is actuated.

The consumer shutoff functionality is made up of the following subfunctions:

• Consumer shutoff with engine running
• Additional consumer shutoff at engine OFF

Consumer shutoff function sequence when engine running:

The consumers are reduced or switched off in the following sequence until the on-board electrical system stabilizes:

1. The heater stages of the PTC heater booster (R22/3) (three each on driver and front passenger sides) are switched off alternately, one after the other, starting with the front passenger-side, by the automatic air conditioning control and operating unit (N22/7) (diesel engine only).
2. The automatic air conditioning control and operating unit reduces actuation of the rear blower motor (M2/1) to 50 % (with code (581) Comfort automatic air conditioning).
3. The automatic air conditioning control and operating unit reduces actuation of the blower motor (A32m1) to 50 %.
4. The automatic air conditioning control and operating unit reduces actuation of the fan motor control unit (N65/2) to 50 %.
5. Deactivation of trailer socket (X58) by rear SAM control unit (with code (550) Trailer hitch).
6. Deactivation of heating stage 3 of seat heater by rear SAM control unit (with code (873) Right and left front seat heaters).
7. Deactivation of rear window heater (R1) by rear SAM control unit.
8. Gradual deactivation of heater stages 2 and 1 of seat heater by rear SAM control unit (with code (873) Right and left front seat heaters).
9. Deactivation of mirror heater (M21/1r1) by left front-door control unit (N69/1) and deactivation of mirror heater (M21/2r1) by right front-door control unit (N69/2).

   Additional consumer shutoff function sequence when engine switched off:

10. Deactivation of residual engine heat utilization function by the automatic air conditioning control and operating unit (with code (581) Comfort automatic air conditioning, not ).
11. Deactivation of rear automatic air conditioning operating unit (N22/4) by automatic air conditioning control and operating unit (with code (581) Comfort automatic air conditioning).
12. Deactivation of interior illumination by front SAM control unit.
13. Deactivation of roof sign, printer, card reader by special-purpose vehicle multifunction control unit (N26/9) (for special-purpose vehicles).
14. Deactivation of all audio components by radio (A2), by radio with auto pilot system (A2/56) or from the COMAND controller unit (A40/3).

Activation of consumers when engine is off 

The consumer is not activated when the voltage recovers. The transmitter key (A8/1) has to be turned to circuit 15C to reset.

Activation of consumers when engine is running 

Function requirements: 

• Engine speed n > 500 rpm and on-board power supply voltage greater than upper voltage threshold (e.g. U = 13.2 V at T = 20 °C) or
• On-board power supply voltage greater than lower voltage threshold and alternating operating rate less than 90 %

Function sequence for actuation of consumers when engine running 

When the function requirements are fulfilled, actuation of the consumers ensues in reverse order to the shutoff, with a waiting time in each instance of t = 2 s.

	On-board computer control electrical function diagram		PE54.10-P-2052-99FAA
	Transmitter key, component description	A8/1	GF80.57-P-6010CW
	Battery sensor component description	B95	GF54.10-P-2100CW
	Front SAM control unit with fuse and relay module, component description	N10/1	GF54.21-P-6070CW
	Rear SAM control unit with fuse and relay module, component description	N10/2	GF54.21-P-6030CW
	Electronic ignition lock control unit, component description	N73	GF80.57-P-6001CW