Testing

A voltmeter (0-20 or 0-30 volt scale), ohmmeter Rotunda Number 059-00010 (needle indicator type), jumper wires and a test lamp (12 volt) are the only tools required to perform an accurate check of the complete charging system. The meters should be calibrated once a year and the date of calibrations stamped on the meter face. It is recommended that this practice be followed by all technicians to maintain their meters at acceptable accuracy.

The tests are divided into "On Vehicle" and "On Bench" test procedures. The "On Bench" procedures are described under the applicable component Section.

Troubleshooting or diagnosis is required before actual service can be made in the electrical system. Even where an obvious condition makes the replacement of a unit necesary, find out why the unit failed. When a problem is diagnosed correctly, unnecessary service is prevented, the time the vehicle is out of service will be decreased, and the service performed will be permanent.

On Vehicle Tests

Before performing charging system tests on the vehicle, note the condition such as: slow cranking, battery dead, top of battery wet, ammeter shows excessive charge at all times or no charge, alternator warning lamp does not come on or never goes out. This information will aid in isolating the part of the system causing the concern. (Refer to Section 31-02 for battery warnings and cautions.)

Figure 5:

Visual Inspection

1. Check the fuse link (Figure 5) located between the starter relay and the alternator. If burned, determine cause, service the system and replace fuse link.

2. The battery must be in proper state of charge. Check the battery posts and battery cable terminals for clean and tight connections. Remove the battery cables (if corroded), clean and install them securely.

3. Check for clean and tight wiring connections on the alternator, regulator and engine.

4. Check the alternator belt tension and tighten to specification (if necessary). Refer to specifications.
Battery Drain Test

1. Connect a 12 volt test lamp in series with the positive terminal of the battery. Test with all switches OFF. Do not be misled by clock time keeping current.

2. If lamp glows, pull fuses, one at a time, and check each circuit for a short. Service wiring harness or components as required.

Indicator Light System Test

Normal Charge Indication - Charge Indicator (Alternator):

With ignition switch OFF - charge indicator (battery symbol) lamp is OFF.

With ignition switch ON (engine not running) - charge indicator (alternator) lamp is ON.

With ignition switch ON (engine running) - charge indicator lamp is OFF.

If the charge indicator lamp does not come on with the ignition ON and the engine not running:

1. Disconnect the wiring connector from the regulator and connect a jumper wire from the wiring connector I terminal to the battery negative post cable clamp. Turn the ignition ON with the engine OFF. If the indicator lamp does not light, check the indicator bulb for continuity and replace the bulb if it is burned out. If the bulb checks good, perform the regulator I Circuit Tests.

2. If the indicator lamp does not light, remove the jumper wire and reconnect the wiring plug to the regulator. Connect the voltmeter negative lead to the battery negative post cable clamp and contact the voltmeter positive lead to the regulator A terminal screw. Battery voltage should be indicated. If battery voltage is not indicated, service the A circuit wiring.

3. If battery voltage is indicated, clean and tighten the ground connections to the engine, alternator and regulator. Tighten loose regulator mounting screws to 1.7-2.8 N-m (15-26 in.lbs.).

4. Turn the ignition ON with engine OFF. If indicator lamp still does not light, replace the regulator.
Ammeter System Test

Normal Charge Indication:

With ignition switch OFF and no electrical load - ammeter should show 0 or center scale.

With ignition switch ON and engine running (fully charged battery) - needle deflects toward charge after starting engine and returns toward center scale in time. With ignition switch OFF and headlamps ON - ammeter should show a discharge. If ammeter does not register a discharge, check for loose connections at the ammeter or an open circuit wire prior to replacing gauge.

General Charging System Test

When performing charging system tests with a voltmeter, turn OFF all lamps and electrical components. Place the transmission in Neutral and apply the parking brake. Test can be performed with Rotunda Starting and Charging Tester 078-00005.

CAUTION: DO NOT MAKE JUMPER WIRE CONNECTIONS EXCEPT AS DIRECTED. TO DO SO MAY DAMAGE REGULATOR. DO NOT GROUND THE REGULATOR A TERMINAL SCREW HEAD.

Base Voltage Test

1. With ignition OFF and no electrical load on, 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 is called base voltage).

No Load Test

1. Connect a tachometer to the engine.

2. Start the engine and increase speed to approximately 1500 rpm. With no other electrical load (foot off brake pedal and vehicle doors closed), the voltmeter pointer should move upward (increase) but not more than 2 volts above the base voltage (the first recorded battery voltage). 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 the proper amount, perform the Load Test below. If the voltage increases over 2.0 volts; perform the Over Voltage Tests that follow. If the voltage does not increase, perform the Under Voltage Tests that follow.
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 2000 rpm. The voltmeter should indicate a minimum of 0.5 volt above the base voltage. If not, perform the under voltage test described below.

If the above tests indicate proper voltage readings, the charging system is operating normally. Use test lamp and check for battery drain.

Over Voltage Tests

If the voltmeter indicates more than 2.0 volts above base battery voltage:

1. With ignition ON and engine OFF, 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. If the voltage difference between the two locations is greater than 0.5 volt, service the A wiring circuit to eliminate the high resistance condition indicated by the excessive voltage drop.

2. If over voltage condition still exists, check for loose regulator to alternator grounding screws. Tighten loose regulator grounding screws to 1.7-2.8 N-m (15-26 in.lbs.).

3. If over voltage condition still exists, connect the voltmeter negative lead to the alternator rear housing. With 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 indicates a defective regulator, grounded brush lead or a grounded rotor coil. Service the entire integral alternator/regulator assembly.

4. If the same voltage reading (battery voltage) is obtained at both screw heads in Step 3 and there is no high resistance in the ground or A+ circuits, then the regulator calibration is high. Replace the regulator.
Under Voltage Tests

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 2.2 ohms. If less than 2.2 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 2.2 ohms, reconnect 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 indicates battery voltage, connect the voltmeter negative lead to the alternator rear housing. Turn the ignition switch ON (engine OFF) and contact 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 and service the I 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 and 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 volts 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.

Regulator I Circuit Tests

1. Disconnect the wiring plug from the regulator. Connect the voltmeter negative lead to the battery ground terminal and the positive lead to the wiring plug I terminal. No voltage should be indicated with the ignition switch OFF. If voltage is indicated, service the I lead from the ignition switch to identify and eliminate the voltage source.

2. Turn the ignition switch to ON. The voltmeter should indicate battery voltage at the wiring plug I terminal. If there is no voltage reading, service the I lead from the ignition switch to the regulator for an open or grounded circuit.

3. If the voltmeter readings in Steps 1 and 2 were normal, check the resistance value of the I circuit resistor. Make the resistance check with the regulator wiring plug disconnected and for indicator light vehicles with the bulb removed. The resistor nominal value is 500 ohms for warning lamp systems and 300 ohms for gauge systems. Replace the resistor if its value is off by more than 50 ohms.

4. Connect the wiring plug to the regulator and replace the bulb for indicator light vehicles.

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 off. Perform No Load and Load Tests before checking for field circuit current 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. 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.