2010 GMC Savana 2500 Cargo Owner's Manual - Page 173

Charging System Light This light comes on briefly when the ignition key is turned to START, but the engine is not running, as a check to show it is working. Voltmeter Gage When the engine is not running, but the ignition is on, this gage shows the battery's state of charge in DC volts. If it does not, have the vehicle serviced by your dealer/retailer. The light should go out once the engine starts. If it stays on, or comes on while driving, there could be a problem with the charging system. A charging system message in the Driver Information Center (DIC) can also appear. See DIC Warnings and Messages on page 4-44 for more information. This light could indicate that there are problems with a generator drive belt, or that there is an electrical problem. Have it checked right away. If the vehicle must be driven a short distance with the light on, turn off 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. 4-27