Charge Lamp/Indicator: Description and Operation

CHARGING INDICATOR

DESCRIPTION
A charging indicator is standard equipment on all instrument clusters. The charging indicator is located near the lower edge of the instrument cluster, to the left of the multi-function indicator display. The charging indicator consists of the International Control and Display Symbol icon for "Battery Charging Condition" imprinted within a rectangular cutout 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 red Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the icon to appear silhouetted against a red field through the translucent outer layer of the overlay when the indicator is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board. The charging indicator is serviced as a unit with the instrument cluster.

OPERATION
The charging indicator gives an indication to the vehicle operator when the electrical system voltage is too low. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and a hard wired input from the generator. The charging indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster detects that the ignition switch is in the On position. Therefore, the LED will always be off when the ignition switch is in any position except On. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn on the charging indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turned to the On position with the engine not running the charging indicator is illuminated by the instrument cluster as a bulb test.
- Generator Input - Each time the cluster detects that the voltage of the generator input is 12.7 volts or lower while the engine is running, the charging indicator will be illuminated. The indicator remains illuminated until the cluster detects that the voltage of the generator input is above 12.7 volts, or until the ignition switch is turned to the Off position, whichever occurs first.

The generator provides a hard wired input to the instrument cluster circuitry on the engine running (D+) circuit. If the instrument cluster turns on the indicator while the engine is running, it may indicate that the charging system requires service. The generator input circuit to the instrument cluster can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the charging system, or the instrument cluster circuitry that controls the charging indicator, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.