General Charging System Tests
When performing charging system tests, turn off all lamps and electrical components. Place the transmission in NEUTRAL and apply the parking brake.
Before performing general charging system tests, make sure the battery is fully charged.
Base Voltage Test
1. With ignition in OFF position and no electrical load, connect the negative lead of the voltmeter to the negative battery cable clamp.
2. Connect the positive lead of the voltmeter to the positive battery cable clamp.
3. Record the battery voltage reading shown on the voltmeter scale. This reading is called the base voltage.
No Load Test
1. Connect a tachometer such as Rotunda Dwell-Tach-Volts-Ohms Tester 059-00010 or equivalent to the engine or ask for someone to help you so the person can look at the tachometer inside the truck so you could use an ordinary multimeter.
2. Start the engine. Increase speed to approximately 1500 rpm. With no other electrical load (foot off brake pedal and doors closed), the voltmeter pointer should move upward (increase), but not more than 2 volts above the base voltage.
NOTE:
The reading should be taken when the voltmeter pointer stops rising. It may take a few minutes to reach this point. If the voltage increases to proper level, perform Load Test. If the pointer continues to rise, perform the Over Voltage Tests. If the voltage does not rise to proper level, perform Under Voltage Tests.
Load Test
1. With the engine running, turn the heater or air conditioner blower motor on (high speed) and headlamps on high beam.
2. Increase the engine speed to approximately 2000 rpm. The voltmeter should indicate a minimum of 0.5 volt above the base voltage. If not, perform the Under Voltage Test.
If the above tests indicate proper voltage readings, the charging system is operating normally. Refer to the following tests if one or more of the readings is different than shown and use a test lamp to check for battery drain.
Over Voltage Test
If the voltmeter indicated more than 2.5 volts above base voltage in the No Load Test, follow these procedures:
1. With the ignition in RUN (engine not running), connect the voltmeter negative lead to the alternator rear housing. Contact the voltmeter positive lead first to the alternator output connection at the starter solenoid and then to the regulator A screw head.
2. If the voltage difference between the two locations is greater than 0.5 volts, service the A wiring circuit to eliminate the high resistance condition indicated by the excessive voltage drop.
3. If the over voltage condition still exists, check for loose regulator and alternator grounding screws. Tighten loose regulator grounding screws to 1.7-2.8 N-m (15-25 in-lb).
4. If the over voltage condition still exists, connect the voltmeter negative lead to the alternator rear housing. With the ignition OFF, contact the voltmeter positive lead first to the regulator A screw head and then to the regulator F screw head. Different voltage readings at the two screw heads indicate a malfunctioning regulator, grounded brush lead or a grounded rotor coil. Service the entire integral alternator/regulator assembly.
5. If the same voltage reading (battery voltage) is obtained at both screw heads in Step 4, and there is no high resistance in the ground or A+ circuit, replace the regulator.
Under Voltage Test
If the voltmeter does not indicate more than 0.5 volt above the base voltage:
1. Disconnect wiring plug from regulator and connect an ohmmeter between the regulator A and F terminal screws. The meter should indicate more than 2.4 ohms. If less than 2.4 ohms is indicated, service the integral alternator/regulator unit for a failed regulator and check the alternator for a shorted rotor or field circuit. Perform the Load Test after servicing.
CAUTION:
Do not replace the regulator before a shorted rotor coil or field circuit has been serviced. Regulator damage could result.
2. If the above ohmmeter reading is greater than 2.4 ohms, connect the regulator wiring plug and connect the voltmeter ground lead to the alternator rear housing. Contact the voltmeter positive lead to the regulator A terminal screw. The meter should indicate battery voltage. If there is no voltage, service the A circuit. Perform Load Test after servicing.
3. If the voltmeter indicates battery voltage, connect the voltmeter ground lead to the alternator rear housing. With the ignition switch OFF, contact the voltmeter positive lead to the regulator F terminal screw. The meter should indicate battery voltage. If there is no voltage, service the integral alternator/regulator unit for an open field circuit. Perform Load Test after servicing.
4. If the voltmeter indicated battery voltage, connect the voltmeter negative lead to the alternator rear housing. Turn the ignition switch to RUN (engine not running), and make contact with the voltmeter positive lead to the regulator F terminal screw. The voltmeter should indicate 1.5 volts or less. If more than 1.5 volts is indicated, perform the I circuit tests. Service the circuit if needed. If the I circuit checks normal, replace the regulator and perform the Load Test.
5. If 1.5 volts or less is indicated, disconnect the alternator wiring plug. Connect a set of 12 gauge jumper wires between the alternator B+ terminal blades and the mating wiring connector terminals. Perform the Load Test, but connect the voltmeter positive lead to one of the B+ jumper wire terminals. If the voltage rises more than 0.5 volt above base voltage, service the alternator-to-starter relay wiring. Repeat the Load Test, measuring the voltage at the battery cable clamps after servicing.
6. If the voltage does not rise more than 0.5 volt above base voltage, connect a jumper wire from the alternator rear housing to the regulator F terminal. Repeat the Load Test with the voltmeter positive lead connected to one of the B+ jumper wire terminals. If the voltage rises more than 0.5 volt, replace the regulator.
7. If the voltage does not rise more than 0.5 volt, service the alternator.
Field Circuit Drain Test
These tests will check for and determine the cause of current drain through the alternator field circuit when the ignition switch is turned to OFF. Perform No Load and Load Tests before checking for field circuit drain.
Connect the voltmeter negative lead to the alternator rear housing for all of the following voltage readings:
1. With the ignition switch turned OFF, contact the voltmeter positive lead to the regulator F terminal screw. The meter should indicate battery voltage if the system is operating normally. If less than battery voltage is indicated, proceed as follows to find the cause of the current drain.
2. Disconnect the wiring plug from the regulator and contact the voltmeter positive lead to the wiring plug I terminal. No voltage should be indicated. If voltage is indicated, service the I lead from the ignition switch to identify and eliminate the voltage source.
3. If no voltage was indicated in Step 2, contact the voltmeter positive lead to the wiring plug S terminal. No voltage should be indicated. If no voltage is indicated, replace regulator.
4. If voltage was indicated in Step 3, disconnect the wiring plug from the alternator rectifier connector. Again, contact the voltmeter positive lead to the regulator wiring plug S terminal. If voltage is still indicated, service the S lead to the alternator plug to eliminate the voltage source. If no voltage is indicated, replace the alternator rectifier assembly.
Regulator S and/or I Circuit Tests
1. Disconnect the wiring plug from the regulator. Connect a jumper wire from the regulator A terminal to the wiring plug A lead. Add a jumper wire from the regulator F screw to the alternator rear housing.
2. With the engine idling and the voltmeter negative lead connected to the battery ground terminal, connect the voltmeter positive lead to the S terminal and then to the I terminal of the regulator wiring plug. The voltage at the S circuit should read approximately one-half that of the I circuit. If voltage readings are normal, remove the jumper wires. Replace the regulator. Connect the wiring plug to the regulator. Repeat the Load Test.
3. If no voltage is present, remove the jumper wires and service the faulty wiring circuit or alternator.
4. Connect the voltmeter positive lead to the positive battery terminal. Connect the wiring plug to the regulator. Repeat the Load Test.
When performing charging system tests, turn off all lamps and electrical components. Place the transmission in NEUTRAL and apply the parking brake.
Before performing general charging system tests, make sure the battery is fully charged.
Base Voltage Test
1. With ignition in OFF position and no electrical load, connect the negative lead of the voltmeter to the negative battery cable clamp.
2. Connect the positive lead of the voltmeter to the positive battery cable clamp.
3. Record the battery voltage reading shown on the voltmeter scale. This reading is called the base voltage.
No Load Test
1. Connect a tachometer such as Rotunda Dwell-Tach-Volts-Ohms Tester 059-00010 or equivalent to the engine or ask for someone to help you so the person can look at the tachometer inside the truck so you could use an ordinary multimeter.
2. Start the engine. Increase speed to approximately 1500 rpm. With no other electrical load (foot off brake pedal and doors closed), the voltmeter pointer should move upward (increase), but not more than 2 volts above the base voltage.
NOTE:
The reading should be taken when the voltmeter pointer stops rising. It may take a few minutes to reach this point. If the voltage increases to proper level, perform Load Test. If the pointer continues to rise, perform the Over Voltage Tests. If the voltage does not rise to proper level, perform Under Voltage Tests.
Load Test
1. With the engine running, turn the heater or air conditioner blower motor on (high speed) and headlamps on high beam.
2. Increase the engine speed to approximately 2000 rpm. The voltmeter should indicate a minimum of 0.5 volt above the base voltage. If not, perform the Under Voltage Test.
If the above tests indicate proper voltage readings, the charging system is operating normally. Refer to the following tests if one or more of the readings is different than shown and use a test lamp to check for battery drain.
Over Voltage Test
If the voltmeter indicated more than 2.5 volts above base voltage in the No Load Test, follow these procedures:
1. With the ignition in RUN (engine not running), connect the voltmeter negative lead to the alternator rear housing. Contact the voltmeter positive lead first to the alternator output connection at the starter solenoid and then to the regulator A screw head.
2. If the voltage difference between the two locations is greater than 0.5 volts, service the A wiring circuit to eliminate the high resistance condition indicated by the excessive voltage drop.
3. If the over voltage condition still exists, check for loose regulator and alternator grounding screws. Tighten loose regulator grounding screws to 1.7-2.8 N-m (15-25 in-lb).
4. If the over voltage condition still exists, connect the voltmeter negative lead to the alternator rear housing. With the ignition OFF, contact the voltmeter positive lead first to the regulator A screw head and then to the regulator F screw head. Different voltage readings at the two screw heads indicate a malfunctioning regulator, grounded brush lead or a grounded rotor coil. Service the entire integral alternator/regulator assembly.
5. If the same voltage reading (battery voltage) is obtained at both screw heads in Step 4, and there is no high resistance in the ground or A+ circuit, replace the regulator.
Under Voltage Test
If the voltmeter does not indicate more than 0.5 volt above the base voltage:
1. Disconnect wiring plug from regulator and connect an ohmmeter between the regulator A and F terminal screws. The meter should indicate more than 2.4 ohms. If less than 2.4 ohms is indicated, service the integral alternator/regulator unit for a failed regulator and check the alternator for a shorted rotor or field circuit. Perform the Load Test after servicing.
CAUTION:
Do not replace the regulator before a shorted rotor coil or field circuit has been serviced. Regulator damage could result.
2. If the above ohmmeter reading is greater than 2.4 ohms, connect the regulator wiring plug and connect the voltmeter ground lead to the alternator rear housing. Contact the voltmeter positive lead to the regulator A terminal screw. The meter should indicate battery voltage. If there is no voltage, service the A circuit. Perform Load Test after servicing.
3. If the voltmeter indicates battery voltage, connect the voltmeter ground lead to the alternator rear housing. With the ignition switch OFF, contact the voltmeter positive lead to the regulator F terminal screw. The meter should indicate battery voltage. If there is no voltage, service the integral alternator/regulator unit for an open field circuit. Perform Load Test after servicing.
4. If the voltmeter indicated battery voltage, connect the voltmeter negative lead to the alternator rear housing. Turn the ignition switch to RUN (engine not running), and make contact with the voltmeter positive lead to the regulator F terminal screw. The voltmeter should indicate 1.5 volts or less. If more than 1.5 volts is indicated, perform the I circuit tests. Service the circuit if needed. If the I circuit checks normal, replace the regulator and perform the Load Test.
5. If 1.5 volts or less is indicated, disconnect the alternator wiring plug. Connect a set of 12 gauge jumper wires between the alternator B+ terminal blades and the mating wiring connector terminals. Perform the Load Test, but connect the voltmeter positive lead to one of the B+ jumper wire terminals. If the voltage rises more than 0.5 volt above base voltage, service the alternator-to-starter relay wiring. Repeat the Load Test, measuring the voltage at the battery cable clamps after servicing.
6. If the voltage does not rise more than 0.5 volt above base voltage, connect a jumper wire from the alternator rear housing to the regulator F terminal. Repeat the Load Test with the voltmeter positive lead connected to one of the B+ jumper wire terminals. If the voltage rises more than 0.5 volt, replace the regulator.
7. If the voltage does not rise more than 0.5 volt, service the alternator.
Field Circuit Drain Test
These tests will check for and determine the cause of current drain through the alternator field circuit when the ignition switch is turned to OFF. Perform No Load and Load Tests before checking for field circuit drain.
Connect the voltmeter negative lead to the alternator rear housing for all of the following voltage readings:
1. With the ignition switch turned OFF, contact the voltmeter positive lead to the regulator F terminal screw. The meter should indicate battery voltage if the system is operating normally. If less than battery voltage is indicated, proceed as follows to find the cause of the current drain.
2. Disconnect the wiring plug from the regulator and contact the voltmeter positive lead to the wiring plug I terminal. No voltage should be indicated. If voltage is indicated, service the I lead from the ignition switch to identify and eliminate the voltage source.
3. If no voltage was indicated in Step 2, contact the voltmeter positive lead to the wiring plug S terminal. No voltage should be indicated. If no voltage is indicated, replace regulator.
4. If voltage was indicated in Step 3, disconnect the wiring plug from the alternator rectifier connector. Again, contact the voltmeter positive lead to the regulator wiring plug S terminal. If voltage is still indicated, service the S lead to the alternator plug to eliminate the voltage source. If no voltage is indicated, replace the alternator rectifier assembly.
Regulator S and/or I Circuit Tests
1. Disconnect the wiring plug from the regulator. Connect a jumper wire from the regulator A terminal to the wiring plug A lead. Add a jumper wire from the regulator F screw to the alternator rear housing.
2. With the engine idling and the voltmeter negative lead connected to the battery ground terminal, connect the voltmeter positive lead to the S terminal and then to the I terminal of the regulator wiring plug. The voltage at the S circuit should read approximately one-half that of the I circuit. If voltage readings are normal, remove the jumper wires. Replace the regulator. Connect the wiring plug to the regulator. Repeat the Load Test.
3. If no voltage is present, remove the jumper wires and service the faulty wiring circuit or alternator.
4. Connect the voltmeter positive lead to the positive battery terminal. Connect the wiring plug to the regulator. Repeat the Load Test.
