Chrysler Full-Size Vans 1989-1998 Repair Guide

Alternator

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TESTING



See Figure 1

Before testing, make sure all connections and mounting bolts are clean and tight. Many charging system problems are related to loose and corroded terminals or bad grounds. Don't overlook the engine ground connection to the body and the alternator drive belt. On some vehicles, it is beneficial to add an additional ground between the engine and the chassis. This may solve many intermittent problems.



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Fig. Fig. 1: Regulator field connections (1 and 2), regulator ground connection (3), and battery positive cable (4)

Voltage Drop Test

Before proceeding, make sure the battery is in good condition and fully charged.

Perform a voltage drop test of the positive side of the circuit as follows:

  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Turn the headlamps, heater blower motor and interior lights on.
  4.  
  5. Bring the engine to about 2,500 rpm and hold it there.
  6.  
  7. Connect the negative voltmeter lead directly to the battery positive terminal.
  8.  
  9. Touch the positive voltmeter lead directly to the alternator B+ output stud, not the nut. The meter should read no higher than about 0.5 volts. If it does, there is higher than normal resistance between the positive side of the battery and the B+ output at the alternator.
  10.  
  11. Move the positive meter lead to the nut and see if the voltage reading drops substantially. If it does, there is resistance between the stud and the nut. The theory is to keep moving closer to the battery terminal, one connection at a time, in order to find the area of high resistance (bad connection).
  12.  

Perform a voltage drop test of the negative side of the circuit as follows:

  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Turn the headlamps, heater blower motor and interior lights on.
  4.  
  5. Bring the engine to about 2,500 rpm and hold it there.
  6.  
  7. Connect the negative voltmeter lead directly to the negative battery terminal.
  8.  
  9. Touch the positive voltmeter lead directly to the alternator case or ground connection. The meter should read no higher than about 0.3 volts. If it does, there is higher than normal resistance between the battery ground terminal and the alternator ground.
  10.  
  11. Move the positive meter lead to the alternator mounting bracket. If the voltage reading drops substantially, you know that there is a bad electrical connection between the alternator and mounting bracket. The theory is to keep moving closer to the battery terminal, one connection at a time, in order to find the area of high resistance (bad connection).
  12.  

Current Output Test

The current output test requires the use of a volt/amp tester with battery load control and an inductive amperage pick-up. Follow the manufacturer's instructions on the use of the equipment.

  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Apply the parking brake and turn off all electrical accessories.
  4.  
  5. Connect the tester to the battery terminals and cable according to the instructions.
  6.  
  7. Bring the engine to about 2,500 rpm and hold it there.
  8.  
  9. Apply a load to charging system with the rheostat on the tester. Do not let the voltage drop below 4 volts.
  10.  
  11. The alternator should deliver to within 2% of the rated output. If the amperage is not within 2% and all other components test okay, replace the alternator.
  12.  

Alternator Isolation Test

On some models, it is possible to isolate the alternator from the regulator by grounding the field terminal. Grounding the field terminal removes the regulator from the circuit and forces full alternator output. On alternators equipped with internal regulators, we recommend replacing the complete assembly if either the alternator or regulator is defective.

Chrysler models have two field terminals, one positive and one negative. The positive terminal will have battery voltage present and the negative terminal will have 3-5 volts less.


WARNING
Do not let the voltage get higher than 18 volts. Damage to electrical circuits may occur.

  1. Connect a voltmeter across the battery terminals so the voltage can be monitored.
  2.  
  3. Start the engine and let it reach normal operating temperature.
  4.  
  5. Connect a jumper lead to a good ground.
  6.  
  7. Locate the field terminal (negative) on the back of the alternator.
  8.  
  9. Momentarily connect the grounded jumper to the field terminal. If the alternator is okay, the voltage will climb rapidly. Disconnect the jumper before the output reaches 18 volts. If the voltage does not rise, replace the alternator. If the voltage rises, the regulator is bad.
  10.  

REMOVAL & INSTALLATION



See Figures 2, 3, 4, 5 and 6

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the accessory drive belt.
  4.  
  5. Label and disconnect the alternator's electrical harness.
  6.  
  7. Remove the alternator mounting bolts.
  8.  
  9. Carefully remove the alternator from the engine.
  10.  

To install:
  1. Position the alternator on the engine.
  2.  
  3. Install the alternator mounting bolts and, on serpentine belt equipped vehicles, tighten to 30 ft. lbs. (41 Nm).
  4.  

On V-belt equipped vehicles, do not yet tighten the alternator mounting bolts.

  1. Connect the electrical harness.
  2.  
  3. Install and properly tension the accessory drive belt. On V-belt equipped vehicles, now tighten the mounting bolts to 30 ft. lbs. (41 Nm).
  4.  
  5. Connect the negative battery cable.
  6.  
  7. Check the alternator for proper operation.
  8.  



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Fig. Fig. 2: On this style of alternator, the battery cable is held in place by a nut



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Fig. Fig. 3: On this style of alternator, the regulator is held in place by two small nuts, and the larger one is for the ground



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Fig. Fig. 4: This alternator is attached with the bolts shown here



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Fig. Fig. 5: Unfasten the attaching bolts and remove the alternator from the bracket



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Fig. Fig. 6: Take care when removing the alternator not to drop it or ground the connections on the back

 
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