ISUZU Amigo/Pick-ups/Rodeo/Trooper 1981-1996

General Information


See Figures 1 and 2

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Fig. Fig. 1: Charging system schematic-1983 Pick-up

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Fig. Fig. 2: Charging system schematic-1992 Rodeo

The alternating current generator (alternator) supplies a continuous output of electrical energy at all engine speeds. The alternator generates electrical energy and recharges the battery by supplying it with electrical current. This unit consists of four main assemblies: two end-frame assemblies, a rotor assembly and a stator assembly. The rotor assembly is supported in the drive end-frame by a roller bearing. These bearings are lubricated during assembly and require no maintenance. There are six diodes in the end-frame assembly. These diodes are electrical check valves that also change the alternating current developed within the stator windings to a direct current (DC) at the output (BAT) terminal. Three of these diodes are negative and are mounted flush with the end-frame, while the other three are positive and are mounted into a strip called a heat sink. The positive diodes are easily identified as the ones within the small cavities or depressions.

The V6 engines experienced engineering changes to improve alternator performance. The alternator in these engines feature a high ampere output per pound of weight. It has an integral regulator but DOES NOT use a diode trio. The stator, rectifier bridge, and rotor with slip rings and brushes are electrically similar to other alternator models.

The regulator voltage varies with temperature and limits system voltage by controlling rotor field current. It switches rotor field current on and off at a fixed frequency of about 400 cycles per second. By varying the on-off time, correct average field current for proper system voltage control is obtained. At high speeds, the on-time may be 10 percent and the off-time may be 90 percent. At low speeds, with high electrical loads, the on-off time may be 90 percent and 10 percent respectively.

The V6 engine alternator is not serviceable. If the alternator is found to be defective, replacement is the only alternative. Even though the other alternators may be serviced, purchasing a new or rebuilt component is often easier and more time-effective.


To prevent damage to the on-board computer, alternator and regulator, the following precautionary measures must be taken when working with the electrical system.

If the battery is removed for any reason, make sure it is reconnected with the correct polarity. Reversing the battery connections may result in damage to the one-way rectifiers. Always check the battery polarity visually. This is to be done before any connections are made to be sure that all of the connections correspond to the battery ground polarity.
When utilizing a booster battery as a starting aid, always connect the positive to positive terminals and the negative terminal from the booster battery to a good engine ground on the vehicle being started.
Never use a fast charger as a booster to start vehicles.
Disconnect the battery cables when charging the battery with a fast charger; the charger has a tendency to force current through the diodes in the opposite direction for which they were designed. This burns out the diodes.
Make sure the ignition switch is OFF when connecting or disconnecting any electrical component, especially on trucks equipped with an on-board computer control system.
Never attempt to polarize the alternator.
Do not use test lights of more than 12 volts when checking diode continuity.
Do not short across or ground any of the alternator terminals.
The polarity of the battery, alternator and regulator must be matched and considered before making any electrical connections within the system.
Never separate the alternator on an open circuit. Make sure all connections within the circuit are clean and tight.
Disconnect the battery ground terminal when performing any service on electrical components.
Disconnect the battery if arc welding is to be done on the vehicle.