Alternator and Regulator Circuit Test
Alternator and Regulator Circuit Test1. Be sure the battery is sufficiently charged and in good condition.
2. Connect a VAT-40 (or equivalent tester), and turn the selector switch to position 1 (starting).
3. Shift to Park or Neutral, 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 there voltage aver 15.1 V?
YES - Replace 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 there voltage less than 13.5 V?
YES - Test and repair the alternator components.
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 - Test and repair the alternator components.
Alternator Control System Test
1. Check for proper operation of the Electrical Load Detector (ELD) by checking that the Malfunction Indicator Lamp (MIL) is off and there is no DTC for ELD failure.
2. Disconnect the alternator 4P connector from the alternator.
3. Start the engine, and turn the headlights (high beam) ON.
4. Measure voltage between the alternator 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 Powertrain Control Module (PCM) 31P connector from the PCM.
7. Check for continuity between the PCM connector terminal C2 and body ground.
Is there continuity?
YES - Repair short in the wire between the alternator and PCM.
NO - Substitute a known-good PCM, and recheck. If prescribed voltage is now available, replace the original PCM.
8. Turn the headlight and ignition switch OFF.
9. Disconnect the PCM 31P connector from the PCM.
10. Check for continuity between the PCM connector terminal C2 and alternator 4P connector terminal No.2.
Is there continuity?
YES - Test the alternator/regulator.
NO - Repair open in the wire between the alternator and PCM.