Alternator

This procedure covers the removal and replacement of the alternator on a 2007 Ram 3500 with the 5.9L Cummins diesel engine.

Warnings

Tools required

Parts

• Alternator (160 amp) × 1 — Use OEM specification or quality aftermarket
• Serpentine belt (if worn or damaged) × 1 — Gates K080906 or equivalent

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn ignition to OFF position and remove key
3. Allow engine to cool completely if recently operated
4. Disconnect negative battery cable and secure away from battery post
5. Photograph or diagram serpentine belt routing for reference

Procedure

1. 1

   Release serpentine belt tension
   Locate the serpentine belt tensioner on the front of the engine. Using a 15mm wrench or serpentine belt tool, rotate the tensioner in the direction that removes tension from the belt (verify correct rotation direction for this tensioner) to release tension on the belt. Slide the belt off the alternator pulley first, then carefully release tensioner pressure. Remove belt from remaining pulleys and set aside.
2. 2

   Disconnect alternator electrical connections
   Locate the main output wire connection on the rear of the alternator (large red wire with nut). Using appropriate socket, remove the nut securing the output wire and carefully pull wire off the stud. Disconnect the small plug connector by pressing the release tab and pulling straight back. Position wires out of the way.
3. 3

   Remove upper alternator mounting bolt
   Locate the upper alternator mounting bolt that passes through the alternator ear into the mounting bracket. Using a socket and ratchet, remove this bolt completely and set aside. This is one of the main mounting bolts that secures the alternator to the mounting bracket.
   Torque spec

   Alternator Mounting Bolts50 Nm (37 lb-ft)
4. 4

   Remove lower alternator pivot bolt
   Locate the lower pivot bolt at the bottom of the alternator. This lower mounting bolt secures the alternator to the bracket; note the automatic tensioner controls belt tension, so this is not a manual adjustment pivot. Remove this bolt completely using appropriate socket and extension if needed for access.
   Torque spec

   Alternator Pivot Bolt25 Nm (18 lb-ft)
5. 5

   Remove alternator from engine
   With both mounting bolts removed, carefully maneuver the alternator out of its mounting position. You may need to tilt it slightly to clear the engine accessories and fan shroud. Support the weight of the alternator as you remove it. Extract the alternator from the engine bay and set on clean work surface.
   ⚠Alternator is heavy; maintain secure grip during removal to prevent dropping onto other components
6. 6

   Inspect mounting bracket and hardware
   With alternator removed, inspect the mounting bracket on the engine for cracks, damage, or loose fasteners. Clean the mounting surfaces with a wire brush to remove any corrosion or debris. Inspect the removed bolts for damage or thread wear; replace if necessary. Check the serpentine belt for cracks, glazing, or excessive wear.
7. 7

   Prepare new alternator for installation
   Remove any protective plastic caps from the new alternator terminals. Compare the new alternator to the old unit to verify correct pulley alignment, mounting hole positions, and electrical terminal locations. Ensure the pulley spins freely and bearings feel smooth with no excessive play.
8. 8

   Install new alternator
   Carefully position the new alternator into the mounting bracket, aligning the mounting holes. You may need to tilt or angle the alternator to maneuver it past surrounding components. Once positioned, align the lower pivot hole first and hand-thread the pivot bolt a few turns to hold the alternator in position.
   Torque spec

   Alternator Pivot Bolt25 Nm (18 lb-ft)
9. 9

   Install upper mounting bolt
   Align the upper mounting ear with the bracket hole and install the upper mounting bolt. Hand-thread the bolt several turns to ensure proper thread engagement. Do not fully tighten yet.
   Torque spec

   Alternator Mounting Bolts50 Nm (37 lb-ft)
10. 10

    Torque alternator mounting bolts
    Using a torque wrench, tighten the alternator mounting bolts to the factory-specified value (verify in service manual; typically approximately 43 Nm / 32 lb-ft for the M10 mounting bolts). Verify both bolts are secure. Verify both bolts are secure and the alternator has no excessive movement in the bracket.
    Torque spec

    Alternator Mounting Bolts50 Nm (37 lb-ft)

    Alternator Pivot Bolt25 Nm (18 lb-ft)
11. 11

    Reconnect electrical connections
    Reconnect the small plug connector to the alternator until it clicks into place. Place the output wire terminal over the stud on the rear of the alternator and install the retaining nut. Tighten the nut securely but do not over-torque (typically 10-12 Nm). Ensure no wires are pinched or contacting moving parts.
12. 12

    Install serpentine belt
    Following your reference photo or diagram, route the serpentine belt around all pulleys except the alternator. Using a 15mm wrench on the tensioner, rotate clockwise to create slack, then slide the belt onto the alternator pulley. Carefully release tensioner pressure to apply proper tension to the belt. Verify belt is properly seated in all pulley grooves.
13. 13

    Reconnect battery and test
    Reconnect the negative battery cable(s) to the battery terminal(s) — note this diesel uses dual batteries — and torque terminal clamps to the specified value (verify in service manual). Start the engine and verify the alternator is operating correctly. Check for proper charging voltage (13.8-14.5 volts with engine running). Listen for unusual noises from the alternator or belt area. Verify battery warning light extinguishes after startup.
    Torque spec

    Battery Terminal Bolts8 Nm (6 lb-ft)

Reassembly

1. Ensure all electrical connections are secure and properly routed away from moving parts
2. Double-check serpentine belt is properly seated in all pulley grooves
3. Verify no tools or parts were left in engine bay

Verification

• Start engine and verify battery warning light turns off within 1-2 seconds
• Use multimeter to check charging voltage at battery terminals: should read 13.8-14.5 volts with engine running at idle
• Turn on electrical loads (headlights, HVAC, radio) and verify voltage remains above 13.5 volts
• Listen for unusual noises from alternator bearing or belt squeal during operation
• Visually inspect serpentine belt for proper alignment and no unusual movement while engine is running

More procedures for this vehicle