Repair Pontiac Mid-size 1974-1983 Repair Guide

Alternator

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Fig. Fig. 1 Charging system schematic



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Fig. Fig. 2 Terminal locations on a typical alternator (generator)

The alternating current generator (alternator) supplies a continuous output of electrical energy at all engine speeds. The belt-driven alternator generates electrical energy and recharges the battery by supplying it with electrical current. The alternator consists of four main assemblies: two end frame assemblies, a stator assembly, and a rotor assembly. The rotor assembly is supported in the drive end frame by a ball bearing and at the other end by a roller bearing. These bearings are permanently lubricated 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 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 component called a heat sink (which serves as a reservoir for excess heat, thus protecting the alternator). The positive diodes are easily identified as the ones within small cavities or depressions.

No periodic adjustments or maintenance of any kind, except for regular belt adjustments, are required on the entire alternator assembly. Alternator output, in amps, is sometimes stamped on the case of each unit, near the mounting hole. Output ratings of the alternators fitted to engines covered here are 37, 42, 55, 57, 61, 63, 70 and 80 amps. Regulator voltages range between 13.6 and 16 volts at 75°.

ALTERNATOR PRECAUTIONS



To prevent serious damage to the alternator and the rest of the charging system, the following precautions must be observed:

  1. When installing a battery, make sure that the positive cable is connected to the positive terminal and the negative to the negative.
  2.  
  3. When jump-starting the car with another battery, make sure that like terminals are connected. This also applies when using a battery charger.
  4.  
  5. Never operate the alternator with the battery disconnected or otherwise on the uncontrolled open circuit. Double-check to see that all connections are tight.
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  7. Do not short across or ground any alternator or regulator terminals.
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  9. Do not try to polarize the alternator.
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  11. Do not apply full battery voltage to the field (brown) connector.
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  13. Always disconnect the battery ground cable before disconnecting the alternator lead.
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REMOVAL & INSTALLATION





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Fig. Fig. 3 Generally, all alternators are mounted in basically the same manner



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Fig. Fig. 4 To remove the alternator, disconnect the battery then pull off the terminal cap



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Fig. Fig. 5 Use a wrench to unfasten the terminal retaining nut ...



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Fig. Fig. 6 ... then remove the terminal connectors from the rear of the alternator



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Fig. Fig. 7 Make sure to unplug all of the alternator electrical connectors



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Fig. Fig. 8 Remove the alternator brace bolt



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Fig. Fig. 9 Use a wrench to loosen ...



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Fig. Fig. 10 ... then remove the alternator mounting bolt



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Fig. Fig. 11 Remove the alternator from the vehicle

  1. Disconnect the battery ground cable to prevent diode damage.
  2.  
  3. Tag and disconnect the alternator wiring.
  4.  
  5. Remove the alternator brace bolt. If the car is equipped with power steering, loosen the pump brace and mount nuts. Detach the drive belt(s).
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  7. Support the alternator and remove the mount bolt(s). Remove the unit from the vehicle.
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  9. To install, reverse the above removal procedure. Alternator belt tension is quite critical. A belt that is too tight may cause alternator bearing failure; one that is too loose will cause a gradual battery discharge. For details on correct belt adjustment, see "Drive Belts" in Chapter One.
  10.  

When adjusting alternator belt tension, apply pressure at the center of the alternator unit, NEVER against either end frame.

TESTING



Preliminary Tests
  1. If you suspect a defect in your charging system, first perform these general checks before going on to more specific tests.
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  3. Check the condition of the alternator belt and tighten if necessary.
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  5. Clean the battery cable connections at the battery. Make sure the connections between the battery wires and the battery clamps are good. Reconnect the negative terminal only and proceed to the next step.
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  7. With the key OFF, insert a test light between the positive terminal on the battery and the disconnected positive battery terminal clamp. If the test light comes on, there is a short in the electrical system of the car. The short must be repaired before proceeding. If the light does not come on, then proceed to the next step.
  8.  

If the car is equipped with an electric clock, the clock must be disconnected.

  1. Check the charging system wiring for any obvious breaks or shorts.
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  3. Check the battery to make sure it is fully charged and in good condition.
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Operational Test

You will need a current indicator to perform this test. If the current indicator is to give an accurate reading, the battery cables must be the same gauge and length as the original equipment.

  1. With the engine running and all electrical systems turned off, place a current indicator over the positive battery cable.
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  3. If a charge of roughly five amps is recorded, the charging system is working. If a draw of about five amps is recorded, the system is not working. The needle moves toward the battery when a charge condition is indicated, and away from the battery when a draw condition is indicated.
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  5. If a draw is indicated, proceed with further testing. If an excessive charge (10-15 amps) is indicated, the regulator may be at fault.
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Output Test
  1. You will need an ammeter for this test.
  2.  
  3. Disconnect the battery ground cable.
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  5. Disconnect the wire from the battery terminal on the alternator.
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  7. Connect the ammeter negative lead to the battery terminal wire removed in step three, and connect the ammeter positive lead to the battery terminal on the alternator.
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  9. Reconnect the battery ground cable and turn on all electrical accessories. If the battery is fully charged, disconnect the coil wire and bump the starter a few times to partially discharge it.
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  11. Start the engine and run it until you obtain a maximum current reading on the ammeter.
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  13. If the current is within ten amps of the rated output of the alternator, the alternator is working properly. If the current is not within ten amps, insert a screwdriver in the test hole in the end frame of the alternator and ground the tab in the test hole against the side of the hole.
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  15. If the current is now within ten amps of the rated output, remove the alternator and have the voltage regulator replaced. If it is still below ten amps of rated output, have the alternator repaired. See the alternator and regulator output chart in this section.
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