Nissan Pick-ups and Pathfinder 1970-1988



See Figures 1, 2, 3, 4 and 5

The alternator converts the mechanical energy supplied by the drive belt into electrical energy by a process of electromagnetic induction. When the ignition switch is turned ON, current flows from the battery through the charging system light (or ammeter) to the voltage regulator, and finally to the alternator. When the engine is started, the drive belt turns the rotating field (rotor) in the stationary windings (stator), inducing alternating current. This alternating current is converted into usable direct current by the diode rectifier. Most of this current is used to charge the battery and to supply power for the vehicle's electrical accessories. A small part of this current is returned to the field windings of the alternator enabling it to increase its power output. When the current in the field windings reaches a predetermined level, the voltage regulator grounds the circuit preventing any further increase. The cycle is continued so that the voltage supply remains constant.

All models use a 12 volt alternator. Amperage ratings vary according to the year and model. 1970-77 models utilize a separate, adjustable regulator, while 1978-88 models have a transistorized, nonadjustable regulator, integral with the alternator.

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Fig. Fig. 1: Exploded view of the alternator-1970-77 (LT-135-13B shown)

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Fig. Fig. 2: Exploded view of the alternator-1978-80

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Fig. Fig. 3: Exploded view of the alternator-1981-88 gasoline engines

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Fig. Fig. 4: Exploded view of the alternator-SD22 engines

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Fig. Fig. 5: Exploded view of the alternator-SD25 engines


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

Never reverse the battery connections. Always check the battery polarity visually. This is to be done before any connections are made to ensure that all of the connections correspond to the battery ground polarity of the truck
Booster batteries must be connected properly. Make sure the positive cable of the booster battery is connected to the positive terminal of the battery which is getting the boost
Disconnect the battery cables before using a fast charger; the charger has a tendency to force current through the diodes in the opposite direction for which they were designed
Never use a fast charger as a booster for starting the truck
Never disconnect the voltage regulator while the engine is running, unless as noted for testing purposes
Do not ground the alternator output terminal
Do not operate the alternator on an open circuit with the field energized
Do not attempt to polarize the alternator
Disconnect the battery cables and remove the alternator before using an electric arc welder on the truck
Protect the alternator from excessive moisture. If the engine is to be steam cleaned, cover or remove the alternator


See Figures 6 and 7

On some models, the alternator is mounted very low on the engine. On these models, it may be necessary to remove the gravel shield and work from beneath the truck in order to gain access to the alternator.

  1. Disconnect the negative battery cable.
  3. Remove the alternator pivot bolt. Push the alternator in and remove the drive belt.
  5. Pull back the rubber boots and disconnect the wiring from the back of the alternator.
  7. Remove the alternator mounting bolt and then withdraw the alternator from its bracket.

To install:
  1. Position the alternator in its mounting bracket and lightly tighten the mounting and adjusting bolts.
  3. Connect the electrical leads at the rear of the alternator.
  5. Adjust the belt tension as detailed in General Information & Maintenance .

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Fig. Fig. 6: Removing the alternator lower mounting bolt

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Fig. Fig. 7: Removing the alternator electrical connection