Chevrolet 10 Series 1968, Service Manual, Page: 437 / 713

ENGINE-ELECTRICAL 6Y-12
F ig . 7 c —Ammeter Method O utput Test Connection
8
. Run engine at 1500 rpm or above for at least 15
minutes of warm-up, then cycle regulator voltage
control (by disconnecting and re-connecting regula­
tor connector) and read voltage.
If voltage is 13.5 to 15.2, the regulator is okay.
a. Disconnect four terminal connector and remove
regulator cover. Then re-connect four terminal
connector and adjust voltage to 14.2 to 14.6
(Refer to Step 6 and fig. 5c).
b. Disconnect four terminal connector and reinstall
regulator cover, then reinstall connector.
c. Continue running engine at 1500 rpm for 5-10
minutes to re-establish r e g u l a t o r internal
temperature.
d. Cycle regulator voltage by disconnecting and
re-connecting regulator connector. Read voltage.
A reading between 13.5 and 15.2 indicates a
good regulator.
CA U TIO N :
Be_ sure four terminal regulator
connector is disconnected when removing or in­
stalling cover.
This is to prevent regulator
damage by short circuits.
SYSTEM COMPONENT TESTS
Delcotron Output Test
Amm eter Method (Fig. 7c)
1. Disconnect the battery ground cable at the battery.
2. Disconnect the red wire at Delcotron battery ter­
minal and connect an ammeter in series between
the wire and terminal.
3. Connect a voltmeter from battery terminal to a good
ground on the generator.
4. Disconnect the F-R terminal connector at the
Delcotron.
5. Connect the jumper wire between Delcotron “ F ” and
battery terminals.
6 . Connect the battery ground cable at the battery.
7. Connect an adjustable carbon pile across the battery
posts.
8 . Start the engine and slowly bring the speed to 1500
rpm and at the same time adjust the carbon pile
load to hold the voltage at 14 volts.
9. Read the amperage and compare with a specifications
chart.
10. Turn off ignition, disconnect battery ground cable,
and remove all test equipment.
11. If the Delcotron meets the test specifications, the
problem is not in the generator.
12. If the Delcotron fails to meet the test specifications,
remove it and perform bench tests and make repair
needed.
Delcotron Diode and Field Test (Fig. 8c)
NOTE: These tests will indicate good, shorted
or open field or shorted diode but will not in­
dicate a failed open diode. If output was low
and following tests show good, refer to service
operations to determine cause and repair.
1. Disconnect battery ground cable at battery.
2. Positive diodes (Test A) connect an ohmmeter be­
tween “ R ” terminal and “ B A T " terminal and note
reading, then reverse the leads at same terminals
and note this reading. Meter should read high re­
sistance in one direction and low in the other.
3. Negative diodes (Test B) connect ohmmeter between
“ R ” terminal and “ GRD” and note reading, then
reverse the leads and note this reading. Meter
should read high in one direction and low in the
other.
NOTE: A high or low reading in both directions
indicates a defective diode.
4. Open Field Check:
a. Connect an ohmmeter from “ F ” terminal to
“ GRD” terminal stud and note reading on the
lowest range scale. Meter should read 7 to 20
ohms.
b. If meter reads zero or excessively high resist­
ance the Delcotron is faulty.
5. If above tests indicate a defective Delcotron, remove
and completely check Delcotron as outlined under
“ Service Operations.”
CHEVROLET TRUCK SERVICE MANUAL
F ig . 8 c —Delcotron Diode and Field Test