Ram Truck 1500, 2500 & 3500 (2006-2008)

Alternator

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Diagnosis & Testing



The charging system should be inspected if:



A Diagnostic Trouble Code (DTC) is set relating to the charging system
 
The charging system warning light (if equipped) is illuminated when the engine is running
 
The "Check Gauges" lamp (if equipped) is illuminated when the engine is running
 
The dashboard voltmeter (if equipped) indicates improper charging (either high or low)
 
The battery is overcharged (electrolyte level is low and/or boiling out)
 
The battery is undercharged (insufficient power to crank the starter)
 

The starting point for all charging system problems begins with the inspection of the battery, related wiring and the alternator drive belt. The battery must be in good condition and fully charged before system testing. If a Diagnostic Trouble Code (DTC) is set, diagnose and repair the cause of the trouble code first.

If equipped, the charging system warning light will illuminate if the charging voltage is either too high or too low. The warning light should illuminate when the key is turned to the ON position as a bulb check. When the alternator starts producing voltage due to the engine starting, the light should go out. A good sign of overly high voltage is lights that burn out and/or burn very brightly. Overcharging can also cause damage to the battery and electronic circuits.

Drive belts are often overlooked when diagnosing a charging system failure. Check the belt tension, check travel limit marks on the tensioner, if fitted. Check belt condition and replace the belt if needed. A loose belt will result in an undercharged battery and a no-start condition. This is especially true in wet weather conditions when moisture causes the belt to become more slippery.

If the vehicle is equipped with a voltmeter, this can sometimes give a clue to belt problems. If the indicated voltage stays low after starting, especially in wet weather, it may indicate that the belt is too loose. Other indications are indicated voltage fluctuations when loads are added or removed from the system as when turning on the air conditioner.

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.  

Diagnostic Trouble Codes



Most charging system problems will set a Diagnostic Trouble Code and light the Malfunction Indicator Lamp (MIL) or similar warning indicator will be lit. On some models it may be possible to access the codes without the special scan tool. Try the following to see if this applies to your vehicle:

  1. Turn the ignition switch ON-OFF-ON-OFF-ON within five seconds.
  2.  
  3. Check the odometer display or note the activity of the MIL. Any stored error codes will be displayed. If the vehicle uses the MIL, it will flash the codes (i.e.: four flashes-pause-seven flashes=47). If the odometer is used, two-digit error codes will be displayed one digit at a time with a short pause between digits.
  4.  
  5. The last display will be "55", indicating that all resident error codes have been displayed.
  6.  
  7. Check any error codes against the following: Error CodeProblem

    12 Battery disconnected
     
    41 Open or shorted field control circuit
     
    44 Shorted battery temp sensor
     
    46 Charging voltage too high
     
    47 Charging voltage too low
     

  8.  

Inspection



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 fuse block 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.  

Removal & Installation



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 and 4.7L 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.  

To install:

  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).
     
    5.7L engine: Tighten bolts to 30 ft. lbs. (41 Nm). Position support bracket to front of generator and install bolt and nuts. Tighten bolt/nuts to 30 ft. lbs. (41 Nm).
     

  4.  
  5. Install or connect the following:

    Alternator harness connectors. Tighten B+ terminal eyelet mounting nut to 8.8 ft. lbs. (12 Nm).
     
    Accessory drive belt
     
    Negative battery cable
     

  6.  

5.9L & 6.7L Diesel Engines

CAUTION
Disconnect both negative battery cables from both batteries before removing battery output wire (b+ wire) from alternator. Failure to do so can result in injury or damage to electrical system.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Disconnect both negative battery cables at both batteries.
  4.  
  5. Remove the alternator drive belt.
  6.  
  7. Remove the upper mounting bracket bolt.
  8.  
  9. Remove the lower mounting bracket bolt and nut.
  10.  
  11. Remove the alternator from engine.
  12.  
  13. Unsnap the plastic insulator cap from B+ output terminal.
  14.  
  15. Remove the B+ terminal mounting nut at rear of generator. Disconnect terminal from alternator.
  16.  
  17. Disconnect field wire connector at rear of alternator by pushing on connector tab.
  18.  

To install:

  1. Position alternator to upper and lower mounting brackets and install upper bolt and lower bolt / nut.
  2.  
  3. Tighten all bolts/nut to 30 ft. lbs. (41 Nm).
  4.  
  5. Firmly snap the field wire connector into rear of alternator.
  6.  
  7. Install the B+ terminal eyelet to generator output stud. Tighten mounting nut.
    WARNING
    When installing a serpentine accessory drive belt, the belt MUST be routed correctly. The water pump may be rotating in the wrong direction if the belt is installed incorrectly, causing the engine to overheat.

  8.  
  9. Install the alternator drive belt.
  10.  
  11. Install both negative battery cables to both batteries.
  12.  

 
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