Dakota, 2001-2005

Alternator

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Diagnosis & Testing




NOTE
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. On some vehicles, it is beneficial to add an additional ground between the engine and the chassis. This may solve many intermittent problems.


NOTE
Alternators must be replaced if defective in any way. No internal service is possible.

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 EVR from the circuit and forces full alternator output. This may help determine whether the problem is the alternator or EVR.


NOTE
Most alternators have two field terminals, one positive and one negative. With the engine running, the positive terminal will have battery voltage present and the negative terminal will have 3-5 volts less. Use a voltmeter to identify the negative terminal before carrying out the following test.


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 circuits are bad.
  10.  

Voltage Drop Test

NOTE
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.  

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.



Wear safety glasses when working on or near the battery.
 
Don-t wear a watch with a metal band when servicing the battery. Serious burns can result if the band completes the circuit between the positive battery terminal and ground.
 
When installing a battery, make sure that the positive and negative cables are not reversed.
 
Be absolutely sure of the polarity of a booster battery before making connections. Connect the cables positive to positive, and negative to negative. Connect positive cables first and then make the last connection to ground on the body of the booster vehicle, so that arcing cannot ignite hydrogen gas that may have accumulated near the battery.
 
Even momentary connection of a booster battery with the polarity reversed will destroy the alternator.
 
Disconnect both battery cables -negative first-before attempting to charge a battery.
 
Never ground the alternator output cable.
 
Be cautious when using metal tools around a battery to avoid creating a short circuit between the terminals.
 
Never ground the field circuit between the alternator and regulator.
 
Never attempt to polarize an alternator.
 
Never operate the alternator with the battery disconnected.
 
Do not short across or ground any alternator terminals.
 
Do not apply full battery voltage to the field connector(s).
 
Always disconnect the battery ground cable before disconnecting the alternator lead.
 
Never subject the alternator to excessive heat or dampness. If you are steam cleaning the engine, cover the alternator.
 
If arc welding is to be done on the car, disconnect the battery and alternator. Disconnect the wiring from the engine controller (PCM). This consists of 14-and 60-pin connectors on most models.
 

Removal & Installation



2.5L, 3.9L & 5.9L Engines
  1. Before servicing the vehicle, please familiarize yourself with safety procedures.
  2.  
  3. Remove or disconnect the following:

    Negative battery cable
     
    Accessory drive belt
     
    Alternator harness connectors
     
    Alternator
     

  4.  
  5. Installation is the reverse of removal. Observe the following torques:


    1. 2.5L engine: 41 ft. lbs. (56 Nm).
    2.  
    3. 3.9L, 5.9L engines: 30 ft. lbs. (41 Nm).
    4.  

  6.  

3.7L & 4.7L Engines
  1. Before servicing the vehicle, please familiarize yourself with safety procedures.
  2.  
  3. Remove or disconnect the following:
    NOTE
    There are 1 vertical and 2 horizontal bolts.



    Negative battery cable
     
    Accessory drive belt
     
    Alternator harness connectors
     
    Mounting bolts and alternator
     



    Click image to see an enlarged view

    Fig. Alternator mounting-3.7L and 4.7L engines

  4.  

To install:

  1. Before servicing the vehicle, please familiarize yourself with safety procedures.
  2.  
  3. Install the alternator and tighten the bolts to the following specifications:

    Vertical bolt and long horizontal bolt: 41 ft. lbs. (56 Nm)
     
    Short horizontal bolt: 55 ft. lbs. (74 Nm).
     

  4.  
  5. Install or connect the following:

    Alternator harness connectors
     
    Accessory drive belt
     
    Negative battery cable
     

  6.  

 
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