Alternator

Remove and replace the alternator on a 1970 AMC Rebel Machine with 390ci V8 engine, including drive belt service and electrical connections.

Warnings

Tools required

Parts

• Alternator (65-amp or upgrade) × 1 — Verify amperage requirements for vehicle accessories
• V-belt (alternator/water pump) × 1 — Measure existing belt or use OEM specification
• Alternator mounting hardware kit (if corroded) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and apply parking brake
2. Allow engine to cool completely if recently operated
3. Open hood and secure with prop rod
4. Disconnect negative battery cable and isolate terminal away from battery post
5. Apply penetrating oil to alternator mounting bolts and adjustment bracket bolt if corrosion is visible

Procedure

1. 1

   Release drive belt tension
   Locate the alternator adjustment bracket bolt on the upper slotted adjustment arm. Loosen the adjustment bracket bolt approximately 3-4 turns using a 9/16" wrench. Push the alternator toward the engine block to create slack in the V-belt. Do not remove the adjustment bolt completely at this stage.
2. 2

   Remove drive belt
   Slip the V-belt off the alternator pulley first, then remove it from the crankshaft and water pump pulleys. Inspect the belt for cracks, glazing, or fraying. Note the belt routing path for reinstallation.
3. 3

   Disconnect electrical connections
   Locate the two electrical connections on the rear of the alternator. Remove the nut securing the battery output wire (large diameter wire with terminal) using a 1/2" wrench and carefully pull the terminal straight off. Disconnect the field wire connector (smaller plug-in connector) by pulling straight out. Mark or photograph wire positions if necessary for reference.
   ⚠Do not allow the battery output terminal to contact the alternator case or other ground points
4. 4

   Remove lower pivot bolt
   Locate the lower alternator pivot bolt that passes through the alternator mounting ear and the lower bracket attached to the engine block. Using a 5/8" socket and wrench, remove the pivot bolt completely. On some units, this bolt also secures a spacer sleeve—retain this for reinstallation. Support the alternator with one hand while removing the bolt.
5. 5

   Remove adjustment bracket bolt and alternator
   Fully remove the upper adjustment bracket bolt from the slotted adjustment arm. Carefully slide the alternator forward and down to clear the mounting bracket and remove it from the engine compartment. Note the position of any washers, spacers, or shims on the mounting points.
6. 6

   Clean mounting surfaces
   Use a wire brush to clean the mounting bracket surfaces on the engine block and the alternator mounting ears. Remove any corrosion, dirt, or old paint to ensure good electrical ground contact. Inspect the adjustment slot for damage or wear.
7. 7

   Bench test new alternator
   Before installation, verify the new alternator spins freely by rotating the pulley by hand. Check that the pulley is properly aligned and the shaft has no excessive play. Compare mounting ear positions and electrical terminal locations with the original unit to ensure correct replacement.
8. 8

   Install replacement alternator
   Position the new alternator into the mounting bracket, aligning the lower pivot point first. Insert the lower pivot bolt with any spacers or washers in their original positions. Thread the bolt by hand but do not fully tighten. Install the upper adjustment bracket bolt through the slotted adjustment arm, leaving it loose for belt tensioning.
9. 9

   Install and tension drive belt
   Route the new or inspected V-belt around the crankshaft pulley and water pump pulley first, then over the alternator pulley. Using a pry bar against the alternator housing (on a reinforced area, not the case seam), lever the alternator away from the engine until proper belt tension is achieved. Belt should deflect approximately 1/2 inch when pressed firmly at the midpoint between pulleys. Hold tension and tighten the adjustment bracket bolt securely.
   ⚠Do not pry against the alternator case seam or stator housing as this can crack the housing
10. 10

    Tighten mounting hardware
    With belt tension set, firmly tighten the lower pivot bolt using a 5/8" socket and wrench. Ensure the alternator does not shift during final tightening. Verify the adjustment bracket bolt remains tight. Check belt tension again after tightening—readjust if necessary.
11. 11

    Reconnect electrical connections
    Reconnect the field wire connector to the alternator until it clicks or seats fully. Install the battery output wire terminal onto the output stud and secure with the retaining nut. Tighten the nut using a 1/2" wrench until snug—do not overtighten as this can damage the stud threads. Ensure no wires contact moving parts or hot exhaust components.
12. 12

    Reconnect battery and perform initial test
    Reconnect the negative battery cable to the battery post and tighten securely. Before starting the engine, turn the ignition key to the ON position (without starting) and verify the alternator warning light on the dashboard illuminates, then extinguishes when the key is turned off. This confirms proper electrical connection.

Reassembly

1. Ensure all electrical connections are secure and wires are routed away from moving parts and heat sources
2. Verify drive belt is properly seated in all pulley grooves and tensioned correctly
3. Double-check that all mounting bolts are tightened and no tools or parts are left in the engine compartment

Verification

• Start the engine and verify the alternator warning light extinguishes immediately
• With engine running at idle, use a voltmeter to measure battery voltage—should read 13.8-14.5 volts indicating proper charging
• Increase engine speed to approximately 2000 RPM and verify voltage remains in the 13.8-14.5 volt range without excessive fluctuation
• Turn on electrical accessories (headlights, heater blower) and verify charging voltage remains stable
• Listen for unusual bearing noise from the alternator during operation
• After test drive, recheck belt tension and alternator mounting bolt tightness

More procedures for this vehicle