Aerostar AWD V6-183 3.0L (1991)
Ammeter Gauge: Description and Operation
The ammeter is an instrument used to indicate current flow into and out of the battery. When electrical accessories in the vehicle draw more current
than the alternator can supply, current flows from the battery and the ammeter indicates a discharge (-) condition. When electrical loads of the vehicle are
less than alternator output, current is available to charge the battery, and the ammeter indicates a charge (+) condition. If battery is fully charged, the
voltage regulator reduces alternator output to meet only immediate vehicle electrical loads. When this happens, ammeter reads zero.
CONVENTIONAL AMMETER
Fig. 1 Conventional Type Ammeter
A conventional ammeter must be connected between battery and alternator in order to indicate current flow. This type ammeter, Fig. 1, consists of a
frame to which a permanent magnet is attached. The frame also supports an armature and pointer assembly. Current in this system flows from the
alternator through the ammeter, then to the battery or from the battery through the ammeter into the vehicle electrical system, depending on vehicle
operating conditions.
When no current flows through the ammeter, the magnet holds the pointer armature so that the pointer stands at the center of the dial. When current
passes in either direction through the ammeter, the resulting magnetic field attracts the armature away from the effect of the permanent magnet, thus
giving a reading proportional to the strength of the current flowing.
SHUNT TYPE AMMETER
The shunt type ammeter is actually a specifically calibrated voltmeter. It is connected to read voltage drop across a resistance wire (shunt) between the
battery and alternator. The shunt is located either in the vehicle wiring or within the ammeter itself.
When voltage is higher at the alternator end of the shunt, the meter indicates a charge (+) condition. When voltage is higher at the battery end of the
shunt, the meter indicates a discharge (-) condition. When voltage is equal at both ends of the shunt, the meter reads zero.
