GDL Bulbs (2006-2013): Design: Headlights

Fig 1: Identifying Headlight

Courtesy of VOLVO CARS CORPORATION

The headlights are operated via the light switch module (LSM). This is on the dashboard at the side of the steering wheel. The light switch module (LSM) is directly connected to the central electronic module (CEM). Low and high beam are operated by moving the left control stalk toward the steering wheel.

In the Bi-Xenon lamps, an actuator motor (solenoid) is used to move a cover in front of the lamp in the lamp housing in order to switch between high and low beam.

In cars with Bi-Xenon lamps, the lamps are powered directly via the central electronic module (CEM) without pulse width modulation.

To detect problems with the low beam, the central electronic module (CEM) reads the power consumption of the circuit. If this falls below a certain threshold value a fault will be indicated. The general warning lamp lights in the driver information module (DIM) and a text message is displayed.

Lighting the headlight 

It normally takes 3 seconds from activation at the light switch with the ignition on to the lamp lighting.

• As with normal headlights, the lamps remain off while the starter motor is cranking and come on once the engine is running.
• On each occasion that voltage is supplied to the ballast 3 attempts, within 1 second, are made to light the lamp.