Operating principles (Freelander 2)

The operation and control of interior lighting can be divided into three main groups.

Front and rear interior lights, footwell lights and cargo area light

The CJB controls the operation of these lamps by applying voltage to both sides of each lamp. By increasing or decreasing the voltage applied to one side of the lamp, the CJB controls the current flowing through the lamp and thus the level of illumination. This function is controlled by a cabin light field effect transistor (FET) which is integrated into the CJB and allows the CJB to smoothly increase and decrease the lamp illumination levels as required. The CJB controls the increase duration over a range of up to 1.3 seconds and the decrease duration over a range of up to 2.6 seconds.

If the vehicle is involved in a collision severe enough to trigger the Supplemental Restraint System (SRS), the Restraint Control Module (RCM) sends a 250Hz 'collision' signal to the CJB. On receiving this signal, the CJB illuminates the front and rear courtesy lamps, footwell lamps and load area lamp for 30 minutes. The CJB switches off the courtesy lamps before the 30 minute period has elapsed if the RCM's collision signal is replaced by a 'normal' 10Hz signal.

Illuminated vanity mirrors and glove compartment

The vanity mirror and glove box lamps are supplied with power from the CJB. When the vanity mirror lamp operation is selected by pressing the relevant switch, a ground circuit is created causing the lamps to illuminate. The vanity mirror lamps are controlled by a microswitch which is integrated into the lamp assembly. When the glove box is opened, the switch contacts are closed, providing a ground for the lamp.

Door and mirror lights

The operation of the door and mirror lights is controlled by the door modules in conjunction with the CJB. The CJB supplies power to the latch switch for each door. When a door is opened, the switch contacts close, providing power to the module for that door. Upon receiving this power, the module turns on the light on that door, providing power and ground.

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The driver and front passenger door modules also control the operation of the mirror lamps. When a valid request is received from the RF receiver, the CJB notifies the driver and front passenger door modules via the medium speed CAN bus. Upon receipt of the CAN bus message, the door module turns on the corresponding mirror lamp, providing ground and power.