Chevrolet 1977 10 Series, Руководство по ремонту, Страница: 231 / 468

ENGINE ELECTRICAL 6D-9
Fig. 6 D -5C --D io d e T rio C hecks
Open Circuit
If lamp fails to light or if ohm m eter reads high when
successively connected between each pair of stator leads, the
windings are open.
Short Circuit
A short in the stator windings is difficult to locate
w ithout special test equipment due to the low resistance of
the windings. However, if all other electrical checks are
norm al and the generator fails to supply rated output, shorted
stator windings are indicated.
Also, look for heat
discoloration on the windings.
Diode Trio (fig. 6D-5C)
W ith the diode trio unit remove from the end frame,
connect an ohm m eter to the single connect and to one of the
three connectors. Observe the reading, then reverse the
ohm m eter leads to the same connectors. A good diode trio
will give one high and one low reading. If both readings are
the same, replace the diode trio. Repeat this test between the
single connector and each of the other two connectors.
NOTE:
There are two diode trio units differing in
appearance used in the generator but they are completely
interchangeable.
The diode trio may also be checked for a grounded brush
lead while still installed in the end frame. Connect an
ohm m eter from the brush lead clip to the end frame as shown
in Step 2, Figure 6D-7C, then reverse the lead connection.
If both readings are zero, check for a grounded brush lead
clip caused by omission of the insulating washer, of the
insulating sleeve over the screw, or damaged insulating
sleeve. Remove the screw to inspect the sleeve. If sleeve or
screw are not grounded, replace regulator.
CAUTION: Do not use high voltage such as 110
volt test lamp to check the diode trio.
BRUSH
HOLDER
RESISTOR
INSULATED
HEAT SINK
G R O U N D E D
HEAT SINK
REGULATOR
INSULATING
WASHER
OHMM ETER
Fig. 6 D -6 C --R e c tifie r B rid g e C hecks
Rectifier Bridge Check (fig. 6D-6C)
Connect an ohm m eter to the grounded heat sink and one
of the three terminals. Then reverse the lead connections to
the grounded heat sink and same terminal. If both readings
are the same, replace the bridge. A good rectifier bridge will
give one high and one low reading. Repeat this same test
between the grounded heat sink and the other two term inals,
and between the insulated heat sink and each of the three
terminals. W hen this is done all six diodes are checked with
two readings taken for each diode.
NOTE:
The diodes are not replaced individually. The
entire rectifier bridge is replaced if one or more diodes
are defective.
CAUTION: Do not use high voltage to check the
rectifier bridge, such as a 110 volt test lamp.
Voltage Reg./Brush Lead Clip Check (fig. 6D-7C)
Connect an ohm m eter from the brush lead clip to the
end frame as shown in Step 1, Figure 6D-7C. Then reverse
lead connections. If both readings are zero, either the brush
lead clip is grounded or the regulator is defective.
A grounded brush lead clip can result from omission of
the insulating washer, omission of the insulating sleeve on the
screw, or a dam aged insulating sleeve. Remove the screw and
inspect the sleeve. If it is satisfactory, replace the regulator
unit.