1997 Chevrolet Astro Owner's Manual - Page 136

Voltmeter When your engine is not running, but the ignition is on (in the RUN position). the gage shows your battery's state of charge in DC volts. Readings in the low warning zone may occur when a large number of electrical accessories are operatingin the vehicle and the engine is left at an idle foran extended period. This condition is normal since the charging system is not able to provide power at full engine idle.As engine speedsare increased, this condition should correct itself as higher engine speeds allow the charging system to createmaximum power. You can only drive fora short time with the readings in either warning zone. If you must drive, turn off all unnecessary accessories. When the ignition 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 either warning zone indicate a possible problem in the electrical system. Have the vehicle serviced as soon as possible. 2-62