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Main beam

Main beam

Description of operation


Main beam is activated by pressing the dipswitch on the steering column when the light switch is in position 2 and the ignition is in the position ON (+15 and +54). DICE activates the main beam relay.

So that DICE can safely determine in which position (0-1-2) the switch (10) is, it uses information from TWICE and its own pin connection.

The parking lights are controlled by TWICE which gives information to the bus (ON/OFF). The message ON corresponds to switch position 1 and the message OFF corresponds to switch positions 1 or 2.

DICE pin 39 is connected to switch pin 2, which corresponds to position 0. DICE pin 15 is connected to switch pin 4, which corresponds to position 2.

From terminal 4 on the light switch (10), voltage +B is fed to pin 15 on the control module. When switch pin 6 (215) feeds DICE pin 41, pin 11 on the control module grounds pin 5 on the main/dipped lamp relay (8) and DICE turns the main beams on. When the relay has closed, the +30 voltage is fed through the relay via the filament monitor (228b) on to fuse 9 (RH main beam) and fuse 8 (LH main beam).

MIU (540) is powered from fuse 8 so that a lamp 47g on the MIU lights up to indicate that the main beams are on.

Filament monitor

The filament monitor is located in the engine bay (relay box). It detects any breaks in the circuit to the lamps by measuring the current in the circuit. In the event of an open circuit, the filament monitor pin 5 grounds pin 10 on the SID unit. SID displays the message “FRONT LIGHT FAILURE”.

Diagnosis

DTC B2280 is generated when there is an open/short circuit to earth in the main beam circuits.

DTCs are not generated if the voltage is below 11V or during diagnostic communication.

Important

When changing a bulb, use one with the right output otherwise the components could be damaged.


Headlamp flasher



The headlamp flasher can be activated irrespective of the position of the ignition switch and light switch using the main/dipped beam stalk switch on the left of the steering wheel.

By moving the dipswitch (215) to its “spring loaded”position, the main beam lamps will be powered with +30 voltage via the filament monitor (228b) and the fuses (8 and 9) to the main beams (11FL and 11FR).

Power from fuse 8 is fed to a lamp in the MIU (540) which is turned on to indicate that the main beams are on.

Headlamp beam-length adjustment

The main and dipped beams are equipped with a function to allow vertical adjustment of the lamp units which in turn varies the length of the light pattern. This control is situated on the dashboard, to the left of the steering wheel. Each headlamp insert is equipped with a motor.

Diagnosis

DTC B2280 is generated when there is an open/short circuit to ground or short circuit to B+.

DTCs are not generated if the voltage is below 11V or during diagnostic communication.