Alternator: Testing and Inspection

Ensure that alternator drive belt is properly adjusted and battery is fully charged before performing the following procedures.

CIRCUIT CONTINUITY TEST

1. Disconnect battery ground cable.
2. Disconnect ``L'' and ``R'' terminals from alternator, then reconnect battery ground cable and place ignition switch in On position.
3. Connect positive lead of a suitable voltmeter to disconnected terminal and negative lead to ground. Observe voltmeter. Voltmeter should read battery voltage. Repeat procedure for remaining terminal. If voltmeter reading is not as specified, check for short or open in circuit.

Fig. 1 Alternator output test connections:

OUTPUT TEST

1. Connect ammeter (A), voltmeter (V) and 30 amp resistor (R) to circuit as shown in Fig. 1.
2. Switch on all accessories, then start engine and allow to run at 3,000 RPM.
3. Vary resistance to increase current load and observe test equipment.
4. Rated output should be reached without voltage dropping below 13 volts.

Fig. 2 Positive side voltage drop test connections:

CIRCUIT VOLTAGE DROP TEST

1. To test positive side voltage drop, proceed as follows:
a. Reconnect ``L'' and ``R'' terminals at alternator, then connect voltmeter (V) to circuit as shown in Fig. 2.
b. Switch on all accessories, then start engine and allow to run at 3,000 RPM.
c. Observe voltmeter.
d. If voltmeter reading obtained in previous step is greater than .5 volt, check positive side of charging circuit for excess resistance and repair as necessary.

Fig. 3 Negative side voltage drop test connections:

2. To test negative side voltage drop, proceed as follows:
a. With ``L'' and ``R'' terminals still connected to alternator, connect voltmeter (V) to circuit as shown in Fig. 3.
b. Switch on all accessories, then start engine and allow to run at 3,000 RPM.
c. Observe voltmeter.
d. If voltmeter reading obtained in previous step is greater than .25 volt, check negative side of charging circuit for excess resistance and repair as necessary.

Fig. 4 Control voltage test connections:

CONTROL VOLTAGE TEST

1. Connect ammeter (A) and voltmeter (V) to circuit as shown in Fig. 4.
2. Start engine, allow to run at 3,000 RPM, then observe ammeter.
3. When ammeter reading falls to between 3 and 5 amps, observe voltmeter reading.
4. Voltmeter reading obtained in previous step should be 13.7 to 14.5 volts. If readings obtained are not within specification, replace voltage regulator.