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ENGINE ELECTRICAL
6D-19
ig. 6D-22J B and X Series With "R" and "K" V8's.
A/C
Fig. 6D-22K B and X Series with "R" and "K" V8's. No
WHEN TENSIONING ALTERNATOR BELT,
POSITION TENSIONING DEVICE AS
POWER STEERING PUMP &
ALTERNATOR MOUNTING BRACKET
31 95
~ g . 6D-22L
A,
B, F and G Series With
"P"
and "2" V8;
8 0
AMP
Generator
ROTOR FIELD WINDING CHECKS
To check for opens, connect the test lamp or ohmmeter
to each slip ring. If the lamp fails to light, or if the ohmmeter
reading is high (infinite), the winding is open (Fig. 6D-24).
Connect test lamp or ohmmeter from one slip ring to
shaft. If lamp lights, or if reading is low, the rotor winding
is grounded.
The winding is checked for short circuits or excessive
resistance by connecting a battery and ammeter in series with
the edges of the two slip rings. The field current at 12 volts
and 80°F should be between 4.0
-
4.5 amperes. As an alternate
method, an ohmmeter can be used, and readings should be
approximately 2.5 to 3.0 ohms. An ammeter reading above
the specified value indicates shorted windings; a reading
below the specified value indicates excessive resistance. If the
resistance reading is below the specified value, the winding
is shorted; if above the specified value the winding has
excessive resistance.
Remember that the winding resistance and ammeter
readings will vary slightly with winding temperature changes.
If the rotor is not defective, but the generator fails to supply
rated output, the defect is in the diode trio, rectifier bridge,
stator, or regulator.
DIODE TRIO CHECK
The diode trio is identified in Figure 6D-25.
To check the diode trio, remove it from the end frame
assembly by detaching the three nuts, the attaching screw,
and removing the stator assembly. Note that the insulating
washer on the screw is assembled over the top of the diode
trio connector. Connect an ohmmeter having a 1 1/2 volt cell,
and using the lowest range scale, to the single connector and
to one of the three connectors (Fig. 6D-26). Observe the
reading. Then reverse the ohmmeter leads to the same two
connectors. If both readings are the same, replace the diode
trio. A good diode trio will give one high and one low reading.
Repeat this same test between the single connector and each
of the other two connectors. Also, connect the ohmmeter to
each pair of the three connectors (not illustrated). If any
reading is zero, replace the diode trio.
NOTE: Figures 6D-25 and 6D-26 illustrate two diode
trios differing in appearance. Either one of these diode
trios may be used in these generators, and the two are
completely interchangeable.
RECTIFIER BRIDGE CHECK
Note that the rectifier bridge has a grounded heat sink
and an insluated heat sink connected to the output terminal.
Also, note the insulating washer located between the
insulated heat sink and end frame on 10-SI generators.
To check the rectifier bridge, connect the ohmmeter to
the grounded heat sink and one of the three terminals (Fig.
6D-27). Then reverse the lead connections to the grounded
heat sink and same terminal. If both readings are the same,
replace the rectifier 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 terminals, and
between the insulated heat sink and each of the three
terminals. This makes a total of six checks, with two readings
taken for each check.
The ohmmeter check of the rectifier bridge, and of the
diode trio as previously covered, is a valid and accurate check.
Do not replace either unit unless at least one pair of readings
is the same.
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