Alternator, Battery, and Starter Connections Check

cen mm 15.01.000

Warning: Batteries release explosive gas as a by-product of their chemical activity. Do not smoke when working around batteries. Put out all flames and remove any source of sparks or intense heat. Make sure the battery compartment is completely vented before disconnecting or connecting the battery cables.

Battery acid is extremely harmful if splashed in the eyes or on the skin. Always wear a face shield and protective clothing when working around batteries.

Damaged, chafed, or kinked wiring can cause electrical short-circuits and lead to fires, causing property damage, injury, or death. Clean, inspect, and maintain wiring and connections carefully.

  1. Disconnect the batteries.
  2. Check the tightness of the alternator bracket fasteners; tighten the fasteners as needed. For torque values, see of the Century Class Trucks Workshop Manual.
  3. See General Description for belt tension specifications. Check the alternator drive belt tension, using a tension gauge at the belt's longest span. Some engines are equipped with more than one alternator belt; check all of them for correct tension. Adjust the belt tension if necessary.
    Engines equipped with a serpentine or poly-V belt have automatic belt tensioners, and do not require belt tension inspection.
  4. Check that all electrical connections at the alternator and starter are clean. Clean and tighten all charging system electrical connections including the connections at the starter B terminal and ground terminal, and where the alternator charging cable terminates.
    Trace and inspect all wiring and cables connected to:

    • Alternator

    • Starter and depopulation studs

    • Batteries

    • Magnetic switch

    • Cab

    • Jump-start studs

    • Battery isolation relays

    • Battery shutoff switches

  5. Check wires and cables for wear, chafing, kinks, discolored insulation, or loose clamps or ties. Find the cause of any problems and repair, replace, and reroute wires and clamps as necessary.
  6. Check the alternator wiring for missing insulation, kinks, and heat damage. Replace or repair as needed.
  7. On the bundled cable that runs from the batteries to the starter, ensure that tie straps are installed at least every 12 inches (300 mm). Replace any missing tie straps, and add tie straps where spacing between them exceeds 12 inches (300 mm).
  8. Ensure that all cables have sufficient slack to allow for engine movement, and that there is no pressure on any wiring connectors.
  9. If any convoluted tubing is damaged, check the wiring inside it. Replace any damaged or missing convoluted tubing.
  10. Clean the cable connector terminals with a wire brush. See of the Century Class Trucks Workshop Manual for troubleshooting instructions, and for adjustment, repair, or replacement instructions.
    1. Clean and tighten the battery ground cable, terminal, and clamps.
    2. Inspect the retainer assembly (or battery hold-downs) and the battery box. Replace worn or damaged parts. Remove any corrosion with a wire brush, and wash with a weak solution of baking soda and water. Rinse with clean water and dry. To prevent rusting, paint the retainer assembly.
    3. Check for and remove any foreign objects such as stones, bolts, or nuts, from the battery box.
    4. After cleaning, connect the cables to the batteries, and tighten them to the torque specifications listed on the battery, generally 10 to 15 lbf·ft (14 to 20 N·m).
    5. Coat the battery terminals with dielectric grease.
  11. Check the terminals on the battery shut-off switch and the magnetic switch. Make sure the terminal connections are clean and tight. Coat the terminal connections with dielectric red enamel after cleaning.
Note:
Parent topic: Alternators and Starters
Document Number: 0000121789
Manual Publication Date: 2025-02-11
Topic Publication Date: 2024-06-04