Turn Signal Indicator: Description and Operation

Two 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 overlay, between the speedometer and the tachometer. Each turn signal indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for "Turn Warning" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents these icons from being clearly visible when their lamps are not illuminated. A green lens behind each cutout in the opaque layer of the causes the icon to appear in green through the translucent outer layer of the overlay when it is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The turn signal indicators are serviced as a unit with the instrument cluster.

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 to the instrument cluster electronic circuit board. The turn signal indicator bulbs are grounded on the instrument cluster electronic circuit board at all times. The turn signal indicator bulbs only illuminate when they are provided with battery current by the turn signal and hazard warning circuitry of the combination flasher through separate left and right turn signal circuit inputs to the instrument cluster; therefore, these indicators can be illuminated, regardless of the ignition switch position.

The turn signal indicators are connected in series between ground and the output of the combination flasher circuitry, but 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 system. For more information on the turn signal and hazard warning system, (Refer to LAMPS/LIGHTING - EXTERIOR - OPERATION - TURN SIGNAL & HAZARD WARNING SYSTEM). The turn signal indicators can be diagnosed using conventional diagnostic tools and methods.