Chevrolet 10 Series 1967, Service Manual

Page: 363 / 605

ENGINE-ELECTRICAL 6Y-15
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.
MAKE 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:
IMPORTANT:
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
winding will be slightly higher than the specified
value. This is true because the specified value
is for an ohmmeter reading directly across the
slip rings.
6
. Disconnect ohmmeter and reconnect the battery
ground strap.
TESTING CIRCUIT RESISTANCE
Excessive resistance in the sensing circuit, consisting
of all field leads and the regulator, can cause an over­
charged battery.
1. Turn on switch but do not start engine.
2. Alternately connect a voltmeter as shown in Part 1
and Part 2 in Figure 16c.
3. If the two voltmeter readings total more than .3
volt, check for excessive resistance in field circuit
leads. If these leads are satisfactory, the field relay
contacts may have excessive resistance. In this case
replace the relay.
VOLTAGE SETTING ADJUSTMENT
A voltage setting not tailored to meet vehicle require­
ments can result in an undercharged or an overcharged
battery. To adjust the voltage setting, proceed as follows:
1. Connect a voltmeter to the adapter as shown in
Figure 14c, Part 1.
2. Connect an ammeter in the circuit at the “ BAT”
terminal on the generator.
3. Turn all accessories off.
4. Operate generator at approximately 3000 rpm (1500-
2 0 0 0
engine rpm).
F ig . 15c—Voltage Tests
CHEVROLET TRUCK SERVICE MANUAL