Charging Circuit Troubleshooting
Charging Circuit TroubleshootingIf the charging system indicator does not come on or does not go off, or the battery is dead or low, test the following items in the order listed below:
- Battery
- Charging system indicator
- Alternator/regulator circuit
- Alternator control system
Charging System Indicator Test
1. Turn the ignition switch ON (II).
Does the charging system indicator came on?
YES - Go to step 2.
NO - Go to step 6.
2. Start the engine.
Does the charging system indicator go off?
YES - Charging system indicator circuit is OK.
NO - Go to step 3.
3. Turn the ignition switch OFF.
4. Disconnect the alternator 4P connector from the alternator.
5. Turn the ignition switch ON (II).
Does the charging system indicator come on?
YES - Turn the ignition switch OFF, and repair the short in the WHT/BLU wire.
NO - Go to step 9.
6. Turn the ignition switch OFF.
7. Disconnect the alternator 4P connector from the alternator.
8. Connect the alternator 4P connector terminal No.3 to body ground with jumper wire. Turn the ignition switch ON (II).
Does the charging system indicator come on?
YES - Go to step 9.
NO - Turn the ignition switch OFF. Check for a blown No.6 (15 A) fuse and a blown charging system light bulb. If the fuse and bulb are OK, repair the open in the BLK/YEL and WHT/BLU wire.
9. Measure the voltage at the No.1 terminal of the alternator 4P connector with the ignition switch ON (II).
Is there battery voltage?
YES - Go to alternator and regulator circuit test.
NO - Repair open in the BLK/YEL wire between the alternator and the under-dash driver's fuse relay box.
Alternator and Regulator Circuit Test
1. Be sure the battery is sufficiently charged.
2. Connect a VAT-40 (or equivalent tester), and turn the selector switch to position 1 (starting).
3. Shift to neutral or park, and start the engine. Hold the engine at 3,000 rpm, with no load until the radiator fan comes on, then let it idle.
4. Raise the engine speed to 2,000 rpm, and hold it there.
Is the voltage over 15.1 V?
YES - Repair the voltage regulator.
NO - Go to step 5.
5. Release the accelerator pedal, and let the engine idle.
6. Make sure all accessories are turned off. Turn the selector switch to position 2 (charging).
7. Remove the inductive pick-up, and zero the ammeter.
8. Place the inductive pick-up over the B terminal wire of the alternator so that the arrow points away from the alternator.
9. Raise the engine speed to 2,000 rpm, and hold it there.
Is the voltage less than 13.5 V?
YES - Repair the alternator components (see page 4-33).
NO - Go to step 10.
10. Apply a load with the VAT-40 until the battery voltage drops to between 12 - 13.5 V.
Is the amperage 75 A or more?
YES - The charging system is OK.
NO - Go to step 11.
11. With the engine speed still at 2,000 rpm, full-field the alternator. Attach the probe to the VAT-40 full-field test lead, and insert the probe into the full field access hole at the back of the alternator. Switch the field selector to the "A (Ground)" position momentarily, and check the amperage reading. Because voltage will rise quickly when the alternator is full-fielded, do not allow the voltage to exceed 18 V: it may damage the electrical system.
Is the alternator output 75 A or more?
YES - Replace the voltage regulator.
NO - Go to alternator control system test.
Alternator Control System Test
1. Check proper operation of the ELD by confirming with the MIL.
2. Disconnect the 4P connector from the alternator.
3. Start the engine and turn the headlights (high beam) ON.
4. Measure voltage between the 4P connector terminal No.2 and the positive terminal of the battery.
Is there 1 V or less?
YES - Go to step 8.
NO - Go to step 5.
5. Turn the headlight and ignition switch OFF.
6. Disconnect the ECM/PCM connector C (31 P).
7. Check for continuity between the ECM/PCM connector terminal C2 and body ground.
Is there continuity?
YES - Repair short in the wire between the alternator and ECM/PCM.
NO - Substitute a known-good ECM/PCM, and recheck.. If prescribed voltage is now available, replace the original ECM/PCM.
8. Turn the headlight and ignition switch OFF.
9. Disconnect the ECM/PCM connector C (31 P).
10. Check for continuity between the ECM/PCM connector terminal C2 and alternator 4P connector terminal No.2.
Is there continuity?
YES - Repair the alternator.
NO - Repair open in the wire between the alternator and ECM/PCM.