Ram 1500, 2500, 3500, 2WD and 4WD, 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.

The following procedures may be used to diagnose the charging system if:



The check gauges lamp (if equipped) is illuminated with the engine running
 
The voltmeter (if equipped) does not register properly
 
An undercharged or overcharged battery condition occurs
 

Remember that an undercharged battery is often caused by:



Accessories being left on with the engine not running
 
A faulty or improperly adjusted switch that allows a lamp to stay on.
 

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.  

Inspection

The Powertrain Control Module (PCM) monitors critical input and output circuits of the charging system, making sure they are operational. A Diagnostic Trouble Code (DTC) is assigned to each input and output circuit monitored by the On-Board Diagnostic (OBD) system. Some charging system circuits are checked continuously, and some are checked only under certain conditions. Refer to Diagnostic Trouble Codes in the Emission and Electronic Engine Control Section for more DTC information. This will include a complete list of DTC's including DTC's for the charging system.

To perform a complete test of the charging system, refer to the appropriate Diagnostic Procedures and the DRB®, or equivalent scan tool. Perform the following inspections before attaching the scan tool.



Inspect the battery condition.
 
Inspect condition of battery cable terminals, battery posts, connections at engine block, starter solenoid and relay. They should be clean and tight. Repair as required.
 
Inspect all fuses in both the fuseblock and Power Distribution Center (PDC) for tightness in receptacles. They should be properly installed and tight. Repair or replace as required.
 
Inspect the alternator mounting bolts for tightness. Replace or tighten bolts if required.
 
Inspect alternator drive belt condition and tension. Tighten or replace belt as required. Refer to Belt Adjustment Procedure in Engine Mechanical.
 
Inspect automatic belt tensioner (if equipped). Belt Adjustment Procedure in Engine Mechanical.
 
Inspect the alternator electrical connections at alternator field, battery output, and ground terminal (if equipped). Also check the alternator ground wire connection at engine (if equipped). They should all be clean and tight. Repair as required.
 

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.  

Installation



The PCM (Powertrain Control Module), or ECM (Diesel) monitors critical input and output circuits of the charging system, making sure they are operational. A Diagnostic Trouble Code (DTC) is assigned to each input and output circuit monitored by the On-Board Diagnostic (OBD) system. Some charging system circuits are checked continuously, and some are checked only under certain conditions.


NOTE
Refer to Diagnostic Trouble Codes in the Emissions and Electronic Engine Controls section for more DTC information. This will include a complete list of DTC's including DTC's for the charging system.

To perform a complete test of the charging system, refer to the Emissions and Electronic Engine Controls section and the DRB® scan tool. Perform the following inspections before attaching the scan tool.

  1. Inspect the battery condition.
  2.  
  3. Inspect condition of battery cable terminals, battery posts, connections at engine block, starter solenoid and relay. They should be clean and tight. Repair as required.
  4.  
  5. Inspect all fuses in both the fuseblock and Power Distribution Center (PDC) for tightness in receptacles. They should be properly installed and tight. Repair or replace as required.
  6.  
  7. Inspect generator mounting bolts for tightness. Replace or tighten bolts if required. Refer to the Generator Removal/Installation section for torque specifications.
  8.  
  9. Inspect generator drive belt condition and tension. Tighten or replace belt as required. Refer to the Engine Mechanical section for procedures.
  10.  
  11. Inspect automatic belt tensioner (if equipped). Refer to the Engine Mechanical section for information.
  12.  
  13. Inspect generator electrical connections at generator field, battery output, and ground terminal (if equipped). Also check generator ground wire connection at engine (if equipped). They should all be clean and tight. Repair as required.
  14.  

3.7L And 4.7L Engines
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Install the alternator and tighten the bolts to the following specifications:

    3.7L engine: Tighten the horizontal bolts to 42 ft. lbs. (57 Nm), then the vertical bolt to 29 ft. lbs. (40 Nm)
     
    4.7L engine: Vertical bolt and long horizontal bolt to 41 ft. lbs. (56 Nm), short horizontal bolt to 55 ft. lbs. (74 Nm)
     

  4.  
  5. Install or connect the following:

    Alternator harness connectors
     
    Accessory drive belt
     
    Negative battery cable
     

  6.  

3.9L, 5.2L, 5.9L And 8.0L Engines
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Install the alternator and tighten the bolts to 30 ft. lbs. (41 Nm).
  4.  
  5. Install or connect the following:

    Alternator harness connectors
     
    Accessory drive belt
     
    Negative battery cable
     

  6.  

5.7L Engines
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Install or connect the following:

    Alternator and tighten the bolts to 30 ft. lbs. (41 Nm)
     
    Support bracket and tighten the nuts and bolt to 30 ft. lbs. (41 Nm)
     
    Alternator harness connectors
     
    Accessory drive belt
     
    Negative battery cable
     

  4.  

Removal & Installation



  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 pivot and mounting bolts/nut
     
    B+ terminal mounting nut from the rear of the alternator, then detach the terminal
     
    Field wire connector from rear of alternator by pushing on the connector tab and pulling the connector out
     
    Alternator
     

  4.  

To install:

Click image to see an enlarged view

Fig. View of the mounting bolt (1), alternator (2), mounting bracket (3) and mounting bolt/nut (4)

View of the mounting bolt (1), alternator (2), mounting bracket (3) and mounting bolt/nut (4)

  1. Install the alternator and tighten the bolts to 30 ft. lbs. (41 Nm).
  2.  
  3. Install or connect the following:

    Alternator harness connectors
     
    Accessory drive belt
     
    Negative battery cable
     

  4.  

3.7L, 4.7L & 5.7L Engines
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove or disconnect the following:
    NOTE
    The 3.7L engine has 1 vertical and 2 horizontal bolts.



    Negative battery cable
     
    Accessory drive belt
     
    Alternator harness connectors
     
    Support bracket nuts and bolt
     
    Mounting bolts and alternator
     

  4.  

3.9L, 5.2L, 5.9L & 8.0L Engines
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove or disconnect the following:

    Negative battery cable
     
    Accessory drive belt
     
    Alternator harness connectors
     
    Alternator
     

  4.  

 
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