Hummer 2009 H2 - Manual (Page 192)

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.
When the engine is running, the gage shows the
condition of the charging system. The charging system
regulates voltage based on the state of the battery for
improved fuel economy and battery life. The gage can
transition from a higher to lower or a lower to higher
reading. This is normal. Readings between the low
and high warning zones indicate the normal operating
range. The gage can also read low during the fuel
economy mode.
Readings in the low warning zone can 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 full power. If there
is a problem with the battery charging system, this light
comes on or the SERVICE BATTERY CHARGING
SYSTEM DIC message displays. See DIC Warnings
and Messages on page 3-56 and Charging System
Light on page 3-35 for more information.
3-36