Generator Testing

NOTE: Battery posts and cable clamps must be clean and tight to ensure accurate meter indications.

When performing charging system tests, turn off all lamps and electrical components. Place transmission in NEUTRAL and apply parking brake.

Generator On-Vehicle Tests - Base Voltage

NOTE: Prior to running this test, turn the headlamps on for 10-15 seconds to remove any surface charge from the battery. Then, wait until the voltage stabilizes before performing the Generator Base Voltage Test. The battery should be at the recommended state of charge.

1. With the ignition OFF and no electrical loads on, connect the ARBST Voltmeter Negative Lead to the battery ground cable clamp.
2. Connect the positive lead of the ARBST to the battery to starter relay cable clamp.
3. Press the MULTIMETER button.
4. Read and record the battery voltage shown on the display. This is called base voltage and will be used in later tests.

Generator On-Vehicle Tests - No-Load
1. Connect the leads of ARBST across the battery terminals.
2. Press the MULTIMETER button.
3. Read the voltage (base voltage).
4. Start the engine and monitor engine speed.
5. Run the engine at 1500 rpm with no electrical load.
6. Read the voltage. The voltage should be in the range of 14.1 to 15.1 volts. If the voltage increase is less than 2.5 volts over the base voltage, perform the Load Test. If there is no voltage increase or the voltage increase is greater than 2.5 volts, perform the Generator On-Vehicle Tests.

Generator On-Vehicle Tests - Load
1. With the engine running, turn on the air conditioner (if equipped), turn the blower motor to high speed and the headlamps to high beam.
2. Increase the engine speed to approximately 2000 rpm. The voltage should increase a minimum of 0.5 volts above the base voltage. If the voltage does not increase as specified, refer to Generator On-Vehicle Tests.

If the voltage increases as specified, the charging system is operating normally. Proceed to battery.

Generator On-Vehicle Tests - Field Circuit Drain
Connect the voltmeter negative lead to the generator rear housing for all of the following voltage readings:
1. With the ignition switch turned to the LOCK position, connect the voltmeter positive lead to the voltage regulator F-terminal. The meter should indicate battery voltage if the system is operating normally. If less than battery voltage is indicated, proceed to Step 2 to find the cause of the current drain.
2. Measure the voltage at the I-terminal with the ignition switch in the LOCK position. If voltage is indicated, REPAIR the I-circuit from the ignition switch to eliminate the voltage source.

Generator On-Vehicle Tests - Drain

WARNING: DO NOT ATTEMPT THIS TEST ON A LEAD-ACID BATTERY THAT HAS RECENTLY BEEN RECHARGED.

CAUTION: Do not crank the engine or operate accessories that draw more than 10 A.

NOTE:
^ The technician must wait approximately 50 minutes after the doors have been opened before performing this test.
^ Many computers draw 10 mA or more continuously.
^ Use an in-line ammeter between the battery positive or negative post and its respective cable.
^ Do not start the vehicle with a clip-on cable.

Check for current drains on the battery in excess of 50 milliamperes with all the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure:
1. Insert the test leads in the input terminals.
2. Turn the switch to mA/A dc.
3. Disconnect the battery terminal and touch probes.
4. Isolate the circuit causing the current drain by pulling out one fuse after another while reading the display.
5. Current reading will drop when the fuse on the bad circuit is pulled.
6. Reinstall the fuse and test components (including connectors) of that circuit to find the defective component(s).

Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment lamp, or luggage compartment lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading will fall to an acceptable level.

Electronic Drains Which Shut Off When the Battery Cable Is Disconnected
1. Repeat Steps 1 through 6 of the drain testing.
2. Without starting the engine, turn the ignition ON for a moment and then OFF. If applicable, wait one minute for the illuminated entry lamps to turn off.
3. Read the current from the multimeter.