Component Tests and General Diagnostics
ON-VEHICLE SERVICE GENERATOR INSPECTIONBefore testing the generator, perform the following checks:
1. Inspect the battery condition.
2. Inspect condition of battery cable and terminals, battery posts, connections at engine block, starter solenoid and relay.
3. Inspect all fuses in both the engine compartment fuse/relay box and the passenger compartment fuse box.
4. Inspect the generator mounting bolts for tightness.
5. Inspect the generator drive belt condition and tension.
6. Inspect connections at generator field, battery output and ground terminals. Check ground connection at engine.
CHARGING SYSTEM RESISTANCE CHECK
This tests will indicate the amount of voltage drop across the generator output wire, from the generator output (B+) terminal to the battery positive post. They will also show the amount of voltage drop from the ground (-) terminal on the generator to the negative battery post.
1. Engage the parking brake, make sure the transaxle is in PARK (A/T) or NEUTRAL (M/T) and start the engine.
2. Set blower control to the maximum position.
3. Turn on headlights and set in high-beam position and turn the vehicle interior lamps on.
4. Bring the engine speed up to 2400 RPM and hold.
5. Touch the DVOM (Digital Voltage and Ohm Meter) negative lead directly to the positive battery post.
6. Touch the DVOM positive lead to the B+ output terminal stud on the generator (not the terminal mounting nut). The output voltage should be no higher than 0.6 V. If the voltage is higher than 0.6 V, touch the DVOM positive lead to the terminal mounting stud nut and then to the wiring connector. If the voltage is now below 0.6 V, look for dirty, loose or poor connection.
7. Touch the DVOM negative lead directly to the negative battery post.
8. Touch the DVOM positive lead to the ground terminal stud on the generator case (not the terminal mounting nut). The voltage should be no higher than 0.3 V. If the voltage is higher than 0.3 V touch the DVOM positive lead to the terminal mounting stud nut and then to the wiring connector. If the voltage is now below 0.3 V, look for dirty, loose or poor connection.
NOTE: A voltage drop test can be performed at each (-) connection in this circuit to locate the excessive resistance. This test can also be performed between the generator case and the engine. If test voltage is higher than 0.3 V, check for corrosion at the generator mounting points or loose generator mounting.
CURRENT OUTPUT TEST
This test will determine if the charging system can deliver its minimum test current (amperage) output. A volt/amp tester equipped with both a battery load control and an inductive type pickup clamp (ammeter probe) will be used for this test. Refer to the operating instructions supplied with the tester.
1. Engage the parking brake, make sure the transaxle is in PARK (A/T) or NEUTRAL (M/T) and start the engine.
2. Bring the engine speed up to 2500 RPM and hold.
CAUTION: This load test must be performed within 15 seconds to prevent damage to test equipment.
3. Slowly adjust the rheostat control (load) on the tester to obtain the highest amperage reading. Do not allow the voltage to drop below 12 V.
NOTE: On certain brands of test equipment, this load will be applied automatically Refer to the operating instructions supplied with the test equipment.
4. The ammeter reading must meet the minimum amps specifications listed on the specifications chart.
5. Turn the load control knob on the tester to the OFF p0sition but continue to hold the engine speed at 2500 RPM. If all circuitry is okay, the amperage should drop below 15 to 20 amps. This may take several minutes with all electrical accessories OFF If amperage does not drop, refer to the Electrical Troubleshooting and check circuitry.
6. Remove the volt/amp tester. If the minimum amperage requirements could not be met, test the generator. If the generator tests okay, check the charging system circuitry.