Light Switch, (10)

Light Switch, (10)

Light switch unit (684), manual headlamp levelling






Light switch unit (684), automatic headlamp levelling (AHL)






Main task
Use to select light setting off, parking, or headlamps. BCM sends the switch status on the bus.

Type
The rotary switch has three positions for the headlamps. The circuit is also equipped with two internal diagnostic resistors.

When the switch is turned all the way to the right (lights off), the switch contacts are open and only the two internal diagnostic resistors (1.8 kohm each) are connected between each connection and ground. If the switch is turned one setting to the left, (parking lights) pin 2 is grounded. With an additional turn to the left (headlamps) pin 1 is grounded.

The light switch also has LEDs to light the symbols and knob.

Connection
The light switch is directly grounded to the body. The 2 pins of the lighting knob are supplied 10.2 V separately via a 1.2 kohm (parking light setting) and a 1.5 kohm (headlamp setting) resistor integrated in BCM. Voltage between each pin and ground is 0 V when the circuit is closed to ground and approx. 6 V (parking light setting) and 5.5 V (headlamp setting) when it is open. If the control module reads 10.2 V, it will interpret it as a break. The LEDs are grounded internally and are supplied with PWM-regulated voltage from BCM.