Turn Signal Lamps, Function

Function
The turn signal switch (S4s1) is connected to the electronic ignition switch (EIS) control module (N73). The 3 positions of the turn signal switch (S4s1) (flashing off, flashing right, flashing left) are read into the electronic ignition switch (EIS) control module (N73) as a voltage coded signal. Due to the voltage coding the switch requires only 2 connections. The input is connected:

- To circuit 15R through a resistor for left flashing
- Directly to terminal 15R for right flashing
- The input is open for flashing off.

When the starter switch is in position "2" the electronic ignition switch (EIS) control module (N73) sends a corresponding message to actuate the flasher lamp group (left/right) for the driver-side signal acquisition and actuation module (SAM) (N10/1) on the CAN buses.

The driver-side signal acquisition and actuation module (SAM) (N10/1) actuates the corresponding group of lamps directly (without additional relay): The corresponding lamp group flashes.

The contact (SAM/lamps) is accomplished via the driver-side fuse and relay module (K40/2). The outputs for all lamps in one lamp group are connected in parallel here.

Turn signal flashing is indicated synchronously in the instrument cluster (A1) by the turn signal indicator lamps A1e1 and A1e2. Simultaneously the audible turn signal indicator (A1h2) in the instrument cluster (A1) is actuated at the flashing frequency. The instrument cluster (A1) receives the required signals via 2 discrete lines which control the indicator lamps directly. (Actuation of the audible turn signal indicator (A1h2) in the instrument cluster is accomplished by decoupling via two diodes.)

Bulb failure indicator
If a bulb in the group of lamps actuated for the turn signals is burned out the flashing frequency and therefore the frequency of the audible turn signal indicator is doubled. The bulb failure is recognized by the driver-side signal acquisition and actuation module (SAM) (N10/1) due to a reduction in the current consumption of the lamp group. Failure of one of the auxiliary turn signal lamps (E22/1), (E22/2) is not recognized due to the lower current consumption of these bulbs!