The easiest way to test the performance of the alternator is to perform a regulated voltage test.
- Start the engine and allow it to reach operating temperature.
- Connect a voltmeter between the positive and negative terminals of the battery.
- Voltage should be 14.1-14.7 volts.
- If voltage is higher or lower than specification, connect a voltmeter between the battery positive (B+) voltage output terminal of the alternator and a good engine ground.
- Voltage should be 14.1-14.7 volts.
- If voltage is still out of specification, a problem exists in the alternator or voltage regulator.
- If voltage is now within specification, a problem exists in the wiring to the battery or in the battery itself.
Alternator Battery (+) Voltage Drop Test
Poor charging system performance may be the result of a dirty, loose, and or corroded electrical connection between the B+ terminal of the alternator and the positive terminal of the battery.
- Connect the positive lead of a multimeter to the positive terminal of the battery. Set the multimeter to the proper volt scale.
- Connect the negative lead of the multimeter to the positive (B+) terminal of the alternator. In most cases, the (B+) terminal will have the thickest (lowest gauge) lead/wire attached to it.
- Operate the engine at 2000 RPM's.
- Load the charging system by operating the headlights and several other high current draw accessories such as the rear defogger or heater blower fan.
- The multimeter show not show a voltage drop over 0.2 Volts. If the voltage drop is higher, clean and or replace the wire as necessary.
Charging system voltage drops can cause below normal charging of the battery.
- To test for a voltage drop on the negative side of the system, connect the negative lead of a multimeter to the negative post on the battery. Set the multimeter to the proper volt scale.
- Attach the positive lead of the multimeter to the alternator's external housing.
- Run the engine at approximately 2000 RPM's.
- Operate the headlights, heater blower fan, rear defogger and any other high current device.
- Maximum voltage drop should not exceed 0.20 volts.
- If the voltage drop exceeds the allowable limit of 0.20 volts, remove the alternator and all of its brackets and clean them. Wire brush all fasteners and their mounting points to ensure a solid connection. Check all ground straps between the cylinder head/block and the chassis of the vehicle. Remove and clean the battery cables. Replace any wires with excessive corrosion that can not be removed.
Excessive AC ripple voltage may be the result of a defective stator with in the alternator. Shorted or open diodes in the rectifier bridge may also cause this problem.
- To test for excessive (AC) ripple voltage, connect a multimeter, that has been set to the proper scale to test (AC) voltage, to the battery terminals. The positive lead of the meter must go to the positive battery post and the negative to the negative battery post.
- Run the engine to approximately 2000 RPM's.
- The maximum voltage must not exceed 0.30 volts.
- Voltage in excess of that amount can cause driveability problems and or damage to powertrain control devices.
- Turn the ignition key to the OFF position.
- Disconnect the negative battery cable.
- Wait at least 90 seconds from the time the negative battery was disconnected to start work.
- Disconnect the electrical harness and wire (and nut) from the alternator.
- Remove the air cleaner (2S-E), if necessary, to gain access to the alternator.
- Unfasten the bolts which attach the adjusting link to the alternator.
- Remove the alternator drive belt from the pulley.
- Unfasten the alternator attaching bolt and then withdraw the alternator from its bracket.
- Mount the alternator on the alternator brackets with the pivot and adjusting bolts.
- Install the drive belt onto the pulley making sure that the grooves on the belt and the grooves on the pulley are properly aligned.
- Adjust the drive belt tension and properly tighten the pivot and adjusting bolts.
- Attach the wire (and nut) and harness to the alternator.
- Connect the negative and starter battery cables.
- Start the engine and allow it warm to warm up. Visually inspect the drive belt and listen for any abnormal vibration. Stop the engine and recheck the belt tension.