GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Alternator

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See Figures 1, 2 and 3

Though the earliest vehicles covered by this guide may be equipped with a generator, most are equipped with an alternator of either external regulator (through early 1970's) or internal regulator (mid 1970's and later) type. Of the internal regulator alternators, there are 2 types used on these vehicles; the SI Delcotron series with 2 terminal integral regulator and the CS Delcotron series with the 4 terminal integral regulator. Once again, most vehicles will be equipped with one type, the SI series alternator, though a few late 1980's vehicles may be equipped with the CS series.

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 ball bearing and at the other end 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 (DC) current 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 small cavities or depressions.



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Fig. Fig. 1: Examples of common alternator mounting- inline 6-cylinder (top), V6 and small block V8 (center) and big-block V8 (bottom)



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Fig. Fig. 2: "SI'' series alternator



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Fig. Fig. 3: "CS'' series alternator

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 terminal
  2.  
  3. When jump-starting the car with another battery, make sure that only 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 an uncontrolled open circuit. Double check to see that all connections are tight.
  6.  
  7. Do not short across or ground any alternator or regulator terminals.
  8.  
  9. Do not try to polarize the alternator.
  10.  
  11. Do not apply full battery voltage to the field (brown) connector.
  12.  
  13. Always disconnect the battery ground cable before disconnecting the alternator lead.
  14.  

CHARGING SYSTEM TROUBLESHOOTING



Alternator With External Regulator

There are many ways in which the charging system can malfunction. Though the source of a problem is often difficult to diagnose, requiring special equipment and a good deal of experience, it is not always the case. If the charging system fails completely and causes the dash board warning light to come on or the battery to become dead, troubleshooting may be easier. To troubleshoot a complete system failure on these vehicles only two pieces of equipment are needed: a test light, to determine that current is reaching a certain point; and a current indicator (ammeter), to determine the direction of the current flow and its measurement in amps.This test works under three assumptions:



The battery is known to be good and fully charged. (If in doubt, either charge and test the battery or substitute a known good battery of the same rating from another vehicles)
 
The alternator belt is in good condition and adjusted to the proper tension.
 
All connections in the system are clean and tight.
 

In order for the current indicator to give a valid reading, the car must be equipped with battery cables which are of the same gauge size and quality as original equipment battery cables.

  1. Turn off all electrical components on the car. Make sure the doors of the car are closed. If the car is equipped with a clock, disconnect the clock by removing the lead wire from the rear of the clock. Disconnect the positive battery cable from the battery and connect the ground wire on a test light to the disconnected positive battery cable. Touch the probe end of the test light to the positive battery post. The test light should not illuminate. If the test light does come on, there is a short or open circuit on the car.
  2.  
  3. Disengage the voltage regulator wiring harness connector at the voltage regulator. Turn the ignition key ON . Connect the wire on a test light to a good ground (engine bolt), then touch the probe end of a test light to the ignition wire connector into the voltage regulator wiring connector. This wire corresponds to the I terminal on the regulator. If the test light goes ON, the charging system warning light circuit is complete. If the test light does not illuminate and the warning light on the instrument panel is ON either the resistor wire, which is parallel with the warning light, or the wiring to the voltage regulator, is defective. If the test light does not come illuminate and the warning light is not ON, either the bulb is defective or the power supply wire from the battery through the ignition switch to the bulb has an open circuit. Connect the wiring harness to the regulator.
  4.  
  5. Examine the fusible link wire in the wiring harness from the starter relay to the alternator. If the insulation on the wire is cracked or split, the fuse link may be melted. Connect a test light to the fuse link by attaching the ground wire on the test light to an engine bolt and touching the probe end of the light to the bottom of the fuse link wire where it splices into the alternator output wire. If the bulb in the test light does not light, the fuse link is melted.
  6.  
  7. Start the engine and place a current indicator on the positive battery cable. Turn off all electrical accessories and make sure the doors are closed. If the charging system is working properly, the gauge will show a draw of less than 5 amps. If the system is not working properly, the gauge will show a draw of more than 5 amps. A charge moves the needle toward the battery, a draw moves the needle away from the battery. Turn the engine off.
  8.  
  9. Disconnect the wiring harness from the voltage regulator at the regulator connector. Connect a male spade terminal (solderless connector) to each end of a jumper wire. Insert one end of the wire into the wiring harness connector which corresponds to the A terminal on the regulator. Insert the other end of the wire into the wiring harness connector which corresponds to the F terminal on the regulator. Position the connector with the jumper wire installed so that it cannot contact any metal surface under the hood. Position a current indicator gauge on the positive battery cable. Have an assistant start the engine. Observe the reading on the current indicator. Have your assistant slowly raise the speed of the engine to about 2,000 rpm or until the current indicator needle stops moving, whichever comes first. Do not run the engine for more than a short period of time in this condition. If the wiring harness connector or jumper wire becomes excessively hot during this test, turn off the engine and check for a grounded wire in the regulator wiring harness. If the current indicator shows a charge of about three amps less than the output of the alternator, the alternator is working properly. If the previous tests showed a draw, the voltage regulator is defective. If the gauge does not show the proper charging rate, the alternator is defective.
  10.  

Delcotron "SI'' Series Alternator With Internal Regulator

See Figure 4

Delcotron "SI'' alternators can be identified by having a two terminal integral voltage regulator connector. Delcotron "CS'' alternators are identified by having a four terminal integral voltage regulator connector on the alternator.

PRELIMINARY CHARGING SYSTEM TESTS
  1. If you suspect a defect in your internal regulator charging system, first perform these general checks before going on to more specific tests.
  2.  
  3. Check the condition of the alternator belt and tighten it if necessary.
  4.  
  5. Clean the battery cable connections at the battery. Make sure the connections between the battery wires and the battery clamps are good.
  6.  
  7. Test the battery cables as outlined in Routine Maintenance of this guide.
  8.  
  9. Check the charging system wiring for any obvious breaks or shorts.
  10.  
  11. Check the battery to make sure it is fully charged and in good condition.
  12.  
  13. If all the previous checks were ok, proceed to the applicable test.
  14.  

CHARGING SYSTEM STATIC TEST
  1. Disconnect the two terminal connector at the alternator.
  2.  
  3. With the ignition ON , connect a voltmeter between the alternator's harness connector terminal 1 (brown wire) and ground.

    If 10 volts or greater is measured go to the next step.
     
    If no voltage is measured, repair the short to ground in the wiring between the generator light in the instrument panel and the alternator connector.
     

  4.  
  5. With the ignition ON , connect a voltmeter between the alternator's harness connector terminal 2 (red wire) and ground.

    If 10 volts or greater is measured, go to the next step.
     
    If no voltage is measured, repair the open or short to ground in the wire between the alternator and the fusible link at the starter solenoid.
     

  6.  
  7. Measure voltage at the alternator between the "BAT'' ring terminal and ground.

    If 10 volts or greater is measured, perform the alternator output test.
     
    If no voltage is measured, repair the open in the wiring.
     

  8.  



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Fig. Fig. 4: "SI'' series alternator schematic

ALTERNATOR OUTPUT TEST

This test can only be performed on Delcotron "SI'' type alternators which have the alternator field ground tab test hole. This test cannot be performed on the Delcotron "CS'' type alternators. An ammeter is required to perform this test.

Delcotron "SI'' alternators can be identified by having a two terminal integral voltage regulator connector. Delcotron "CS'' alternators are identified by having a four terminal integral voltage regulator connector on the alternator.

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the battery terminal on the alternator.
  4.  
  5. Connect the ammeter's negative lead to the battery wire disconnected in the previous step.
  6.  
  7. Reconnect the negative battery cable and turn on all lights and accessories. Leave the lights and accessories on for a minute or two to draw down the battery a little before going on to the next step.
  8.  
  9. Start the engine and run it until you obtain a maximum current reading on the ammeter. Make sure all accessories are ON (blower motor, wipers, air conditioning, high beam headlights, etc.). Record the reading and compare to the alternator's rated output, which is stamped onto the frame of the alternator. If the reading is:

    Within 10 percent of the rated output, the alternator is good.
     
    Not within 10 percent of the rated output go to the next step.
     

  10.  
  11. With the engine running at moderate speed and all accessories ON, ground the alternator field. This can be done by inserting a insulated screwdriver in the alternator field test hole and allowing the screwdriver shaft to touch the alternator case. Again record the reading and compare to the alternator's rated output, which is stamped onto the frame of the alternator. If the reading is:

    Within 10 percent of the rated output, the alternator's regulator is most likely defective.
     
    Not within 10 percent of the rated output, the problem is with either the alternator's field winding, diode trio, rectifier bridge or stator.
     

  12.  

Delcotron "CS'' Altnerator With Internal Regulator

See Figure 5

Delcotron "SI'' alternators can be identified by having a two terminal integral voltage regulator connector. Delcotron "CS'' alternators are identified by having a four terminal integral voltage regulator connector on the alternator.

PRELIMINARY CHARGING SYSTEM TESTS
  1. If you suspect a defect in your internal regulator charging system, first perform these general checks before going on to more specific tests.
  2.  
  3. Check the condition of the alternator belt and tighten it if necessary.
  4.  
  5. Clean the battery cable connections at the battery. Make sure the connections between the battery wires and the battery clamps are good.
  6.  
  7. Test the battery cables as outlined in Routine Maintenance of this guide.
  8.  
  9. Check the charging system wiring for any obvious breaks or shorts.
  10.  
  11. Check the battery to make sure it is fully charged and in good condition.
  12.  
  13. If all the previous checks were ok, proceed to the applicable test.
  14.  

STATIC TEST
  1. Disconnect the four terminal connector at the alternator.
  2.  
  3. With the ignition ON , connect a voltmeter between the alternator's harness connector terminal "L'' (brown wire) and ground.

    If 10 volts or greater is measured go to the next step.
     
    If no voltage is measured, repair the short to ground in the wiring between the generator light in the instrument panel and the alternator connector.
     

  4.  
  5. With the ignition ON , connect a voltmeter between the alternator's harness connector terminal "I'' (red or pink wire) and ground.

    If 10 volts or greater is measured, go to the next step.
     
    If no voltage is measured, repair the open or short to ground in the wire between the alternator and the fusible link at the starter solenoid.
     

  6.  
  7. Measure voltage at the alternator between the "BAT'' ring terminal and ground.

    If 10 volts or greater is measured, the problem is in the alternator. Remove the alternator for repair or replacement.
     
    If no voltage is measured, repair the open in the wiring.
     

  8.  



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Fig. Fig. 5: "CS'' series alternator schematic

REMOVAL



See Figures 6, 7, 8, 9, 10 and 11

  1. Disconnect the negative battery cable to prevent diode damage and prevent the chance of shorting the battery cables.
  2.  
  3. Tag and disconnect the alternator wiring. Use a small screwdriver to release the locktab on the alternator connector, then use a wrench to loosen the stud nut and disconnect the terminal wiring.
  4.  
  5. Loosen the alternator lower though-bolt, then remove the alternator brace/adjuster bolt.
  6.  
  7. On some vehicles equipped with power steering, it may be necessary to loosen the pump brace and mount nuts, then detach the pump drive belt.
  8.  
  9. Pivot the alternator inward and remove the drive belt from the pulley.
  10.  
  11. Support the alternator and remove the lower mount bolt(s), then remove the unit from the vehicle.
  12.  



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Fig. Fig. 6: Use a small screwdriver to release the locktab on the alternator connector



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Fig. Fig. 7: Use a wrench to loosen the wiring terminal stud nut located under a small rubber boot on the rear of the alternator



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Fig. Fig. 8: Loosen the lower alternator mounting through-bolt (pivot bolt)



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Fig. Fig. 9: Remove the alternator bracket/adjuster bolt



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Fig. Fig. 10: Pivot the alternator inward and remove the drive belt from the pulley



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Fig. Fig. 11: Support the alternator and remove the through-bolt, then remove the alternator from the vehicle

INSTALLATION AND BELT ADJUSTMENT



For more details on belt adjustment procedures, please refer to Routine Maintenance of this information.

  1. Position the alternator in the vehicle and install, but do not fully tighten, the lower mount through-bolt(s).
  2.  
  3. Pivot the alternator inward and position the drive belt over the pulley.
  4.  
  5. If removed earlier, install the power steering pump drive belt, adjust the tension and tighten the pump fasteners.
  6.  

Determine belt tension at a point halfway between the pulleys by pressing on the belt with moderate thumb pressure while the component is held or pried outward from the engine. The belt should deflect about1/2in. at the halfway point if the distance between the pulleys (measured from the center of each pulley) is 13-16 in. The belt should deflect1/4in. if the distance is 7-10 in. Once the proper deflection is achieved, the adjuster bolt should be tightened.

  1. Pivot the alternator outward in order to properly adjust the belt tension, then tighten the pivot bolt and the lower though-bolt(s).
  2.  
  3. Install the alternator wiring as noted during removal. If equipped, make sure the rubber boot is properly positioned over the stud nut terminal at the rear of the alternator.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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