Turn Signal Indicator: Description and Operation
TURN SIGNAL INDICATORSTwo turn signal indicators, one right and one left are standard equipment on all instrument clusters The turn signal indicators are located near the upper edge of the instrument cluster, the left one is left of the tachometer, and the right one is right of the speedometer. Each turn signal indicator consists of an International Control and Display Symbol icon for "Turn Warning" imprinted on a green lens. Each lens is located behind a dedicated cutout in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents these icons from being clearly visible when they are not illuminated. The icons appear silhouetted against a green field through the translucent outer layer of the overlay when the indicator is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The turn signal indicator lenses are serviced as a unit with the instrument cluster lens, hood and mask unit.
The turn signal indicators give an indication to the vehicle operator that the turn signal (left or right indicator flashing) or hazard warning (both left and right indicators flashing) have been selected and are operating. These indicators are controlled by two individual hard wired inputs from the combination flasher circuitry to the instrument cluster electronic circuit board. Each turn signal indicator bulb is grounded on the instrument cluster electronic circuit board at all times. Therefore, each bulb can be illuminated regardless of the ignition switch position. Each bulb only illuminates when it is provided with battery current by the combination flasher in the Junction Block (JB). The turn signal indicators will be illuminated for the following reasons:
- Turn Signal-On Input - Each time a turn signal indicator bulb receives battery current pulses from the turn signal circuitry of the combination flasher, the requested turn signal lamps and turn signal indicator will be flashed on and off. The selected turn signal lamps and turn signal indicator will continue to flash on and off until the combination flasher stops feeding them battery current pulses, or until the ignition switch is turned to the Off position, whichever occurs first.
- Hazard Warning-On Input - Each time the turn signal indicator bulbs receive battery current pulses from the hazard warning circuitry of the combination flasher, all turn signal lamps and both turn signal indicators will be flashed on and off. All turn signal lamps and both turn signal indicators will continue to flash on and off until the combination flasher stops feeding them battery current pulses, regardless of the ignition switch position.
The turn signal indicators are connected in parallel with the other turn signal circuits. This arrangement allows the turn signal indicators to remain functional, regardless of the condition of the other circuits in the turn signal and hazard warning systems. The combination flasher outputs to the instrument cluster turn signal indicator inputs may be diagnosed using conventional diagnostic tools and methods.