GM Blazer/Jimmy/Typhoon/Bravada 1983-1993 Repair Guide

Alternator

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The alternator used in the charging system of S/T trucks starting in 1983 is the SI integral regulator alternator. The alternator will be one of the following types: 10-SI or 12-SI. Differences between the types are output current ratings, along with the drive end and slip ring end bearing stack up.

Starting in 1986, the CS-130 alternator was used in production. The CS-130 features 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 the SI model alternators.

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 CS-130 alternator is not serviceable. If an alternator is found to be defective, replacement is the only alternative. Even though the SI alternators may be serviced, purchasing a new or rebuilt component is often easier and more effective.

ALTERNATOR PRECAUTIONS



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

  1. 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.
  2.  
  3. 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.
  4.  
  5. Never use a fast charger as a booster to start vehicles.
  6.  
  7. 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.
  8.  
  9. 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.
  10.  
  11. Never attempt to polarize the alternator.
  12.  
  13. Do not use test lights of more than 12 volts when checking diode continuity.
  14.  
  15. Do not short across or ground any of the alternator terminals.
  16.  
  17. The polarity of the battery, alternator and regulator must be matched and considered before making any electrical connections within the system.
  18.  
  19. Never separate the alternator on an open circuit. Make sure all connections within the circuit are clean and tight.
  20.  
  21. Disconnect the battery ground terminal when performing any service on electrical components.
  22.  
  23. Disconnect the battery if arc welding is to be done on the vehicle.
  24.  

DIAGNOSIS



SI Alternator

See Figures 1, 2 and 3

A charge indicator lamp is used in most trucks to signal when there is a fault in the charging system. This lamp is located in the gauge package and is used in diagnosis. A voltmeter may be used instead of the charge indicator lamp in diagnosis.



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Fig. Fig. 1: Sectional view of the SI model alternator



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Fig. Fig. 2: Schematic of the SI model alternator



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Fig. Fig. 3: SI model alternator diagnosis and testing

CS-130 Alternator

See Figures 4 and 5

  1. Check drive belt(s) for wear and tension. Check wiring for obvious damage.
  2.  
  3. Go to Step 7 for vehicles without a charge indicator lamp.
  4.  
  5. With the ignition switch ON and the engine stopped, the lamp should be ON. If not, detach the wiring harness at the generator and ground the "L" terminal lead.
  6.  
  7. If the lamp illuminates, replace the alternator. If the lamp does not illuminate, locate the open circuit between the grounding lead and the ignition switch. Check the lamp, it may be open.
  8.  



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Fig. Fig. 4: Sectional view of the CS model alternator



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Fig. Fig. 5: Schematic of the CS model alternator

  1. With the ignition switch ON and the engine running at moderate speed, the lamp should be OFF. If not, stop the engine, then turn the switch ON and detach the wiring harness at the alternator.
  2.  
  3. If the lamp goes out, replace the alternator. If the lamp stays ON, check for a grounded "L" terminal wire in the harness.
  4.  
  5. Determine if the battery is undercharged or overcharged.
  6.  
  7. An undercharged battery is evidenced by slow cranking or a dark hydrometer.
  8.  
  9. An overcharged battery is evidenced by excessive spewing of electrolyte from the vents.
  10.  
  11. Detach the wiring harness connector from the alternator.
  12.  
  13. With the ignition switch ON , and the engine not running, connect a voltmeter from ground to the "L" terminal in the wiring harness, and to the "I" terminal, if used.
  14.  
  15. A zero reading indicates an open circuit between the terminal and the battery. Repair the circuit as necessary.
  16.  
  17. Engage the harness connector to the alternator and run the engine at moderate speed with accessories OFF.
  18.  
  19. Measure the voltage across the battery. If above 16 volts, replace the alternator.
  20.  
  21. Connect an ammeter at the alternator output terminal, run the engine at moderate speed, turn ON all the accessories and load the battery with a carbon pile to obtain maximum amperage. Maintain voltage at 13 volts or above.
  22.  
  23. If the output is within 15 amps of the rated output of the alternator (stamped on the alternator case), the alternator is good. If the output is not within 15 amps, replace the alternator.
  24.  

REMOVAL & INSTALLATION



V-Belt Equipped Engines

See Figures 6, 7, 8, 9, 10, 11, 12 and 13

  1. Disconnect the negative battery cable to prevent diode damage and prevent the chance of shorting the battery cables.
  2.  
  3. Remove other components as necessary to gain access to the alternator.
  4.  
  5. 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.
  6.  



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Fig. Fig. 6: Depress the locktab and disengage the wiring connector from the alternator



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Fig. Fig. 7: Pull back the rubber boot, then loosen and remove the ring terminal retaining nut

  1. Loosen the alternator lower though-bolt, then remove the alternator brace/adjuster bolt.
  2.  
  3. Pivot the alternator inward and remove the drive belt(s) from the pulley.
  4.  

On some early model vehicles, the heater hose(s) may interfere with alternator travel. If you are unable to pivot the alternator sufficiently to free the drive belt(s), partially drain the cooling system, disconnect and reposition the heater hose(s) for the necessary clearance.

  1. If equipped, remove the rear mounting bolt from the engine alternator bracket.
  2.  
  3. Support the alternator and remove the lower mount bolt(s), then remove the unit from the vehicle.
  4.  

To install:
  1. Position the alternator in the vehicle and install, but do not fully tighten, the lower mounting and/or through bolt(s).
  2.  
  3. If equipped, install the rear mounting bolt to the engine alternator bracket.
  4.  



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Fig. Fig. 8: With the nut removed, the ring terminal may be disconnected from the alternator



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Fig. Fig. 9: Loosen the mounting/pivot bolt(s)

  1. Pivot the alternator inward and position the drive belt(s) over the pulley.
  2.  

If the driven component has two drive belts, the belts should be replaced in pairs to maintain proper tension. It is better to have belts too loose than too tight, because overtightened belts will lead to bearing failure, particularly in the water pump and alternator. However, loose belts may place an extremely high impact load on the driven components due to the whipping action of the belt.

  1. Move the accessory toward or away from the engine until the tension is correct. You can use a wood hammer or tool handle as a lever, but do not use anything metallic.
  2.  
  3. Tighten the bolts and re-check the tension.
  4.  



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Fig. Fig. 10: Remove the alternator adjusting bolt



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Fig. Fig. 11: Pivot the alternator inward and remove the drive belt(s) from the pulley

  1. 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.
  2.  
  3. Connect the negative battery cable.
  4.  
  5. If new belts have been installed, run the engine for a few minutes, then re-check and readjust as necessary.
  6.  



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Fig. Fig. 12: Support the alternator and remove the mounting/pivot bolt(s)



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Fig. Fig. 13: Remove the alternator from the vehicle

Serpentine Belt Engines

See Figure 14

Unlike the pivoting alternator used on many of the earlier vehicles covered by this guide, later model vehicles equipped with a serpentine drive belt utilize an alternator that is bolted into a fixed position.

  1. Disconnect the negative battery cable.
  2.  
  3. For the 4.3L (VIN W) engine, remove the air inlet duct assembly, then remove the nut retaining the radiator hose brace to the back of the alternator.
  4.  
  5. If equipped, remove the retainers, then remove the brace from the engine and/or the alternator.
  6.  
  7. Disconnect the battery terminal boot wiring from the back of the alternator, then disengage the regulator wiring connector.
  8.  
  9. Carefully relieve the serpentine drive belt tension, then remove the belt from the alternator pulley. Do not allow the tensioner to snap back into position once the belt is off the pulley.
  10.  
  11. Support the alternator and remove the mounting bolts (usually 2) from either side of the alternator, then remove the alternator from the vehicle.
  12.  

To install:
  1. Position the alternator in the vehicle and loosely install using the mounting bolts.
  2.  
  3. If equipped, loosely install the brace to the engine and/or alternator.
  4.  
  5. Tighten the retaining bolts:
  6.  
  7. For the 2.5L engine, tighten the nut on the lower mounting bolt to 37 ft. lbs. (50 Nm), the upper mounting bolt to 25 ft. lbs. (34 Nm) and the rear bolt to 20 ft. lbs. (27 Nm).
  8.  
  9. For the 2.8L engine, tighten the lower mounting bolt to 26 ft. lbs. (35 Nm) for engines through 1990 or to 37 ft. lbs. (50 Nm) for 1991 and later engines. Tighten the upper mounting bolt to 18 ft. lbs. (25 Nm), then as applicable, tighten the AIR pump bracket bolt, rear brace bolt and/or stud nut to 18 ft. lbs. (25 Nm) and the rear brace-to-bracket nut to 37 ft. lbs. (50 Nm).
  10.  
  11. For the 4.3L engine, tighten the left or front alternator bolt to 36 ft. lbs. (50 Nm), the right or rear alternator bolt to 18 ft. lbs. (25 Nm), the brace bolt to 18 ft. lbs. (25 Nm) and/or the brace nut (VIN W engine only) to 22 ft. lbs. (30 Nm), as applicable.
  12.  
  13. Connect and secure the alternator wiring.
  14.  
  15. Carefully relieve the serpentine drive belt tension and position the belt over the alternator pulley, then slowly release the tensioner into position.
  16.  
  17. If equipped, install the air inlet duct assembly.
  18.  
  19. Connect the negative battery cable.
  20.  



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Fig. Fig. 14: Common alternator mounting - 4.3L engine

BELT ADJUSTMENT



For information on V-belt and serpentine drive belt installation, removal and adjustments, please refer to General Information & Maintenance of this guide.

 
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