GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 1998 🢒 Unit Repair 🢒 Engine 🢒 Engine Electrical 🢒 Charging System Check

When the charging system is operating normally, the charge indicator lamp will come on when the ignition switch is turned on and will go out when the engine starts. If the lamp operates abnormally, or if an undercharged or overcharged battery condition occurs, diagnose and repair the charging system. Refer to . Remember that an undercharged battery is often caused by accessories being left on overnight, or by a rear compartment or instrument panel compartment lamp that stays on.

Noise from a generator may be caused by the following:

    • Improper routing of hoses, wiring or shielding against the generator housing.
    • A loose drive pulley
    • Loose mounting bolts
    • Worn or dirty bearings
    • A faulty diode
    • A faulty stator
    • Brush/slip ring friction

Important: To avoid damage to the electrical equipment, observe the following precautions:

   • Do not reverse the connections to the generator.
   • Do not short across, or ground any of the terminals in the charging circuit, except as directed by the instructions.
   • Do not attempt to hot wire the generator by connecting B+ voltage to any of the generator 4-way connector terminals. Use only an approved test harness as described in these instructions.
   • Never disconnect the output terminal while the generator is operating.
   • Use only approved Metri-pack terminal probe adapters to connect the meter leads and the jumper wires to the connector terminals. Using improper adapters will damage the connector terminals and cause charging system or test harness failure.
   • Before connecting a charger or a booster battery to the vehicle battery, review the battery charging procedure. Refer to .

Before testing the generator inspect the following :

    • Battery. Make sure that the vehicle battery is in good condition and fully charged. Refer to .
    • Built-in hydrometer in the battery. The green eye must be showing in the hydrometer.
    • The voltage across the battery terminals with all loads OFF should be above 12 volts. Refer to .
    • Make sure that the battery connections are clean and tight.
    • Drive belt for damage or looseness. Refer to .
    • Wiring harness at the generator. Make sure that the harness connector is tight and latched. Make sure that the output terminal of the generator is connected to the vehicle battery positive generator lead.
    • All the charging system related fuses and electrical connections for damage or looseness. Refer to .

Generator

Tools Required

J 41450-B J 41450-B

To diagnose a CS generator use the following procedure:

  1. Turn the ignition switch OFF. Turn all the electrical accessory loads OFF.

    2. Important: Make sure the ammeter clip is placed for the entire generator output to pass through the clip. Refer to . If the circuits are split so that any of the current can pass through parallel circuits the generator output reading on the inductive ammeter will not be accurate.

  2. Turn the load in the carbon pile load tester all the way OFF. Connect a load test across the battery terminals.
  3. Install the inductive ammeter around the output wire(s) of generator.
  4. Perform the universal tester self-test procedure per the manufacturer's instructions to verify proper operation of the tester.
  5. Connect the red alligator clip of the tester to the generator output terminal. Connect the black clip to the metal generator housing. The green POWER lamp on the tester should light. If the green POWER lamp lights, go to step 8. If the POWER lamp does not light, go to step 6.
  6. Use a digital multimeter to check the voltage between the generator output terminal and the battery negative terminal. If reading is B+ voltage, go to step 7. If not, check for an open fusible link or an open condition in the generator output wiring and repair as necessary. If the tester's green POWER lamp now lights when connected per step 5, go to step 8. If no open condition was found or the green POWER lamp still does not light, go to step 7.
  7. With the tester still connected as described in step 5, connect a jumper wire between the generator metal housing and the battery negative terminal. The green POWER lamp on the tester should light. If the green POWER lamp does light, check the ground path from the generator housing to the battery negative terminal for an open conditions and repair as necessary. If the tester's green POWER lamp now lights, go to step 8. If the lamp does not light, return to step 1 and repeat the procedure, including the tester self-test procedure.
  8. With tester still connected as described in step 5, disconnect the 4-way generator connector from the generator and connect the matching connector on the tester to the generator. The red DIAGNOSTIC lamp on the tester should light. If the DIAGNOSTIC lamp does light, go to step 10. If the DIAGNOSTIC lamp does not light, go to step 9.
  9. Disconnect the 4-way tester connector from the generator. With the ignition key in RUN (engine stopped), use a fused jumper lead (with a 5 A fuse) and Metri-pack 150 terminal probe adapter to ground the L terminal (cavity B) in the vehicle harness 4-way connector. If the fuse does not blow, replace the generator. If the fuse blows, diagnose and repair the L terminal circuit (225) for direct short to B+ or mis-wired/no resistance condition, then replace the generator. Fix the wiring before replacing the generator. Refer to .
  10. Turn OFF all the electrical accessories and close the doors to be sure all the loads are off. With the tester connected as described in step 8, start the engine and let the engine idle briefly. (Note that the vehicle's generator control circuits are bypassed during this test, and the charge indicator in the instrument cluster will not operate normally.) After the engine starts, the red DIAGNOSTIC lamp on the tester should not be lit. If the red DIAGNOSTIC lamp is still lit, replace the generator. If the red DIAGNOSTIC lamp is not lit, go to step 11.
  11. Increase the engine speed to 2500 RPM. The red DIAGNOSTIC lamp on the tester should not light. If the red DIAGNOSTIC lamp lights, replace the generator. If the red DIAGNOSTIC lamp is not lit, go to step 12.
  12. With the engine speed still at 2500 RPM, turn the load on the carbon pile load tester to ON and adjust until the generator output is at the Load Test value. Refer to . If the red DIAGNOSTIC lamp on the tester lights with the generator operating at or below the load test output value, replace the generator. If the red light does not light and the load test value is attained, the generator is good. DO NOT replace the generator. Go to step 13.
  13. Turn the carbon pile load tester load to OFF and stop the engine. Remove the generator tester, ammeter, and load tester from the vehicle. Reconnect the 4-way harness connector to the generator. Be sure the connector is fully seated and latched.
    14. • If the customer has commented about erratic or high voltage from a generator that uses an S terminal connection, be sure to check the S terminal circuit (cavity D in the harness connector) for intermittent or high resistance connections.
    •  If the customer has commented about a battery that loses charge over a period of time, refer to .