2005 Chevrolet Express Van Owner's Manual - Page 138

Charging System Light This light should come on briefly when you turn on the ignition, before starting the engine, as a check to show you it is working. Voltmeter Gage When your engine is not running, but the ignition is on (in the RUN position), this gage shows your battery's state of charge in DC volts. After the engine starts, the light should go out. If it stays on or comes on while you are driving, you may have a problem with your charging system. It could indicate a problem with the generator drive belt, or some other charging system problem. Have it checked right away. Driving while this light is on could drain your battery. If you must drive a short distance with this light on, it helps to turn off all your accessories, such as the radio and air conditioner. When the engine is running, the gage shows the condition of the charging system. Readings between the low and high warning zones indicate the normal operating range. Readings in the low warning zone may occur when a large number of electrical accessories are operating in the vehicle and the engine is left at an idle for an extended period. This condition is normal since the charging system is not able to provide full power at engine idle. As engine speeds are increased, this condition should correct itself as higher engine speeds allow the charging system to create maximum power. 3-28