HIGH BEAM INDICATOR
DESCRIPTION
A high beam indicator is standard equipment on all instrument clusters. This indicator is located near the upper edge of the cluster overlay, between the tachometer and the speedometer.
The high beam indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for High Beam in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. A blue Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the indicator to appear in blue through the translucent outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board.
The high beam indicator is serviced as a unit with the instrument cluster.
OPERATION
The high beam indicator gives an indication to the vehicle operator whenever the headlamp high beams are illuminated. In certain markets where required, the high beam indicator also gives an indication when the optional light bar lamps are illuminated. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received from the Body Control Module (BCM) over the Programmable Communications Interface (PCI) data bus.
The high beam indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will allow this indicator to operate whenever the instrument cluster receives a battery current input on the fused B(+) circuit. Therefore, the LED can be illuminated regardless of the ignition switch position. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the high beam indicator for the following reasons:
- High Beam Indicator Lamp-On Message - Each time the cluster receives an electronic high beam indicator lamp-ON message from the BCM the high beam indicator will be illuminated. The high beam indicator remains illuminated until the cluster receives a lamp-OFF message from the BCM.
- Light Bar Lamps-On Message - This function of the high beam indicator applies only to vehicles equipped with the optional light bar lamps and manufactured for certain markets where it is required. Each time the cluster receives an electronic light bar lamps-ON message from the BCM the high beam indicator will be illuminated. The high beam indicator remains illuminated until the cluster receives a lamps-OFF message from the BCM.
- Actuator Test - Each time the cluster is put through the actuator test, the high beam indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The BCM continually monitors the exterior lighting (multi-function) switch and the optional light bar lamp switch to determine the appropriate outputs to the headlamp low beam, headlamp high beam, and light bar lamp relays. The BCM then sends the proper lamp-ON and lamp-OFF messages to the ElectroMechanical Instrument Cluster (EMIC).
For proper diagnosis of the headlamp system, the light bar lamp system, the BCM, the EMIC, the PCI data bus or the electronic communication related to high beam indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.