Chevrolet 10 Series 1968, Service Manual

Page: 440 / 713

ENGINE-ELECTRICAL 6Y-15
POSITIVE
END CASE
FRAME DIODES
CASE HEAT
DIODES SINK
BRUSH GREASE
ASSEMBLY ROTOR ASSEMBLY RESERVOIR
SLIP
RINGS
GREASE
RESERVOIR
BALL
BEARING
BALL
BEARING
DRIVE
END
FRAME
SLIP RING
END FRAME
STATOR
ASSEMBLY
F ig . 13c — 130 AM P Series 4 D , Type 150 Delcotron
purpose of isolating the unit that is causing the charging
system malfunction. Like any other system, we make a
continuity check, voltage setting test, and circuit re­
sistance test.
In order to easily make these tests, it is necessary to
use an adapter at the regulator harness connector.
Notice that the adapter shown in the illustrations has
three different length test leads. This is only for pur­
poses of differentiating during this program.
M ake The Test as Follows:
1. Make usual visual checks.
2. Make the battery light load test.
3. Make a complete charging system test as follows:
a. Test the field relay.
b. Check the field circuit.
c. Check generator output. (Same as on any other)
d. Check circuit resistance.
e. Test and adjust the voltage setting.
To Check The Field Relay
1. Connect a voltmeter at test adapter as shown in
Figure 14c, Part 1.
2. Make sure the switch is off, then read voltmeter.
a. Voltmeter reads zero - relay O.K.
b. Voltmeter reading battery voltage - relay points
stuck closed or relay damaged.
3. Turn the switch on and read the voltmeter.
a. Voltmeter reads battery voltage - relay O.K.
b. Voltmeter reads zero - relay winding bad or
open circuit in wiring to relay.
4. Make necessary repairs and recheck.
To Test The Generator Field Circuit
1. Connect the voltmeter to test adapter as shown in
Figure 14c, Part 2.
2. Turn the switch on and read the voltmeter.
a. If voltmeter reads 1-2 volts less than battery
voltage, field is O.K. - check generator output.
b. If voltmeter reads zero, an open circuit in the
regulator itself is indicated.
c. If voltmeter reads battery voltage, look for an
open field winding or a shorted regulator.
Test The Field as Follows:
IM PORTANT: The regulator defect may have
been caused by a defective generator field.
Check the field as follows before installing the
new regulator.
1. Turn the switch off and disconnect the battery ground
strap.
2. Disconnect the adapter from the regulator.
3. Connect an ohmmeter to the adapter as shown in
Figure 15c.
4. If the ohmmeter reads high, there is an open, or
excessive resistance in the field winding, or in lead.
5. If the ohmmeter reads low the winding is shorted
or grounded.
NOTE: The specified resistance value can be
determined by dividing the voltage by the cur­
rent given in specifications. Since the reading
is taken through the adapter, leads, brushes and
slip rings, the ohmmeter reading on a good field
CHEVROLET TRUCK SERVICE MANUAL