Dipped beam (standard) RPO TT4

The headlamps consist of a bulb with single filament or an electric arc bulb of the type HID (high-intensity discharge) plus a ballast unit on each side of the car, which produces main beam and dipped beam.

The headlamps can be lit in three different ways.

• When the headlamp switch is set to the ON position, for normal use.
• When the headlamp switch is set to the AUTOMATIC position for automatic headlamp control.
• When the headlamp switch is set to the AUTOMATIC LIGHTING position and the windscreen wipers are ON in daylight conditions, after a 6 s delay.

The Body Control Module (BCM) regulates the headlamps based on the input described above. When a request for dipped beam is received, BCM feeds B+ through the headlamp dipped bean relay for the left-hand headlamp and through the daytime running lamp - right relay for the right-hand headlamp. This then feeds B+ to the dipped beam headlamps so that they come on. When a request for main beam is received, BCM grounds the control circuit for the headlamp main beam relay. This supplies current to the coil in the headlamp main beam relay so that the relay switch closes. It then feeds B+ to both of the main beam headlamps through the fuses for the left and right main beam so that the main beam headlamps come on.

The headlamps can be reset from right-hand traffic to left-hand traffic by moving a lever on the headlamps down and from left-hand traffic to right-hand traffic by moving a lever on the headlamps up.