Chevrolet 70 1969 Series, Руководство по ремонту

Страница: 739 / 913

ENGINE ELECTRICAL 6Y-24
M ake checks in following sequence:
1. Disassemble the generator leaving only the shell, sta­
tor, and heat sinks with diodes assembled (fig. 7).
2. Cut the stator lead nearest the light relay wire (No. I
cut), and the stator lead which is farthest from the
light relay wire (No. 2 cut). Cuts are shown on Figure
7.
3. Using either test lamp or ohmmeter, check the No. I
positive diode starting with one test probe to “ BAT”
terminal and the other test probe to the light relay
wire, then reverse this connection.
a. If using test light and it lights in both checks,
the diode is defective. When checking a good
diode, test lamp will light only when connected
in one direction.
b. If using an ohmmeter, and both readings are very
low or if both readings are very high, the diode
is defective. A good diode will indicate one low
reading and one high reading.
4. To check the No. 1 negative diode, place one of the
probes on the light relay wire and the other probe on
F ig u re 7 — T e stin g D io d e s
the negative heat sink. Reverse this connection to
check this diode.
5. To check the No. 2 positive diode, touch one probe to
the No. 1 cut stator lead which comes from the diode,
not the end of the lead that goes to stator, and the
other probe to ground on stator shell; reverse this
connection to determine the state of diode.
6. To check No. 2 negative diode, place one probe to the
No. 1 cut stator lead and ground the other probe on
the negative heat sink then reverse connections to de­
termine state of this diode.
7. To check the No. 3 positive diode, place one probe on
No. 2 cut stator lead (diode end) and ground the
other probe on the positive heat sink, then reverse the
connections to determine state of diode.
8. To check the No. 3 negative diode, place a probe on
the No. 2 cut stator lead (diode end) and the other
probe on the negative heat sink. Reverse these con­
nections to determine state of this diode,
NOTE: If all six diodes check as being good,
then the stator should be checked. In order to
check stator the third lead from tthe stator must
also be cut. This will make it not necessary to
disturb the epoxy and solder at the No. 1 neg­
ative diode. Proceed to check stator as directed
previously under "Stator Checks."
9. If any one or more diodes were found defective re­
place diodes as directed later under “ R epair” (See
“ Diode Replacem ent” ).
Special Testers. Special testers are available which op­
erate without disconnecting stator. When using this type
of equipment, follow manufacturer's recommendations.
NOTE: Use only rosin core (60 percent tin, 40
percent lead) solder to resolder leads after
m aking electrical checks.
CAPACITOR CHECK
The capacitor is mounted to generator end frame and
capacitor lead is connected to insulated heat sink (fig. 3).
Since the capacitor rating is only 0.5 microfarads, it is
impractical to test the capacitance with conventional
equipment, however, when generator is disassembled for
overhaul a check should be made to be sure the insulation
between elements is not permitting a current leak to
ground.
Check can be made with 12-volt test lamp or a 1 -
1/2-volt ohmmeter. Connect one test lead to capacitance
lead and other lead to capacitor case (fig. 9). Wiggle the
“ pig tail” lead while observing ohm m eter or test lamp. If
capacitor is good, the ohmm eter will show infinite (high)
resistance or a test lamp will not glow during test.
Any capacitor which allows current leakage as indicat­
ed by low ohmm eter reading or glowing test lamp must
be replaced.
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK S H O P M A N U A L