GMC 1995 Safari Owner's Manual page 113

Voltmeter
Standard Cluster
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1
Digital Cluster
.. . .. .
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. 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 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.
On the digital cluster, a box around the voltmeter symbol will begin the
flash when the charging system needs service.
You can only drive for a short time with the readings in either warning zone.
If you must drive, turn off all unnecessary accessories.
Readings in either warning zone indicate a possible problem in the electrical
system. Have the vehicle serviced as soon as possible,
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