Control Voltage; Output; Diodes Bench Test; Field Diodes Bench Test - Ford VSG-411 Service Manual

4903
Charging System
4-03
CONTROL VOLTAGE
1. Disconnect the battery ground lead, then disconnect the alter-
nator wiring plug.
2. Connect Voltmeter Ammeter and jumper as shown in Figure
2. Use caution to prevent grounding the terminals to the
alternator housing.
FIG. 2 Control Voltage Test
3. Connect battery ground lead and start engine.
4. Run engine at 3,000 r-pm. Note ammeter reading. When this
falls to between 3 and 5 amps, check the voltmeter reading. It
should be 13.7 to 14.5 volts. If reading is outside specified
limits, replace regulator.
5. Turn ignition switch off and disconnect battery ground lead.
Disconnect test equipment.
6. Connect alternator wiring plug and battery ground lead.
OUTPUT
1. Connect Voltmeter Ammeter and Rheostat as shown in Figure
3. Use caution to prevent grounding the terminals to the
alternator housing.
FIG. 3 Output Test
2. Start engine, run it at 3,000 rpm. Vary resistance to increase
load current. Rated output should be reached without voltage
dropping below 13 volts, If rated output cannot be reached
check alternator.
BENCH TESTS
DIODES
Remove the rectifier assembly from the alternator as outlined
under Disassembly. Set the ohmmeter Multiply By knob at 10 and
calibrate the meter.
To test one set of diodes, contact one probe to the diode plate as
shown in Figure 4 and contact each of the three diode pin terminals
with the other probe. Reverse the probes and repeat the test. All
diodes should show a low reading of about 70 ohms in one
direction, and an infinite reading (no needle movement) with the
probes reversed. Repeat the preceding tests for the other set of
diodes.
If the meter readings are not as specified, replace the rectifier
assembly.
FIG. 4 Diode Test
FIELD DIODES
To test the field diodes contact the negative probe to the brush
terminal as shown in Figure 5 and contact each of the three
positive diode pin terminals with the positive probe. All diodes
should show a low reading of about 70 ohms. Reverse the probes
and all diodes should show an infinite reading (no needle
movement).
If the meter readings are not as specified, replace the rectifier
assembly.
FIG. 5 Field Diode Test
A- Positive Diodes
B-
Brush Terminal