Chevrolet 1977 light duty truck, Service Manual

Page: 607 / 861

UNIT REPAIR
D I S A S S E M B L Y (FIG. 6 D - 1 C )
1. Hold generator in a vise, clamping the mounting
flange lengthwise.
2. Remove the four thru-bolts and separate the slip ring
end frame and stator assembly from the drive end and rotor
assembly by prying apart with a screwdriver at the stator slot.
N OTE: A scribe mark will help locate the parts in the
same position during assembly.
3. Place a piece of tape over the slip ring end frame
bearing to prevent entry of dirt and other foreign material,
and also a piece of tape over the shaft at the slip ring end.
CAUTION: Brushes m a y drop onto the rotor shaft
a n d become contam inated with bearing lubricant.
Clean brushes prior to installing with a non-toxic
cleaner such as trichlorethylene or a so ft dry cloth.
4. Remove the stator lead attaching nuts and separate
stator from end frame.
N OTE: A t this point, with the two end frames separated
the stator disconnected and the rotor removed electrical
checks of the rotor, rectifier bridge, stator and diode trio
brush lead clip may be made w ithout further
disassembly. Refer to the specific checks as outlined in
this section.
5. Remove screw attaching diode trio to brush holder
assembly and remove diode trio from end frame.
6. Remove the rectifier bridge attaching screw and the
"BAT" term inal screw, and disconnect the capacitor lead.
Remove rectifier bridge from the end frame.
7. Remove two attaching screws, and remove brush
holder and regulator assemblies.
N OTE: Two insulators are assembled over the top of the
brush retaining clips and the two screws have special
insulating sleeves over the screw body.
8. Remove retaining screw and capacitor from end of
frame.
9. Remove slip ring end frame bearing (if necessary).
Refer to bearing replacement covered in this section.
10. Remove pulley retaining nut and slide washer,
pulley, fan and spacer from shaft.
a. Single groove pulley-place 15/16" box wrench on the
shaft nut and insert a 5/16" alien wrench into the shaft end
hole to hold the shaft while removing the nut (fig. 6D-8C).
b. Double groove pulley-place a 15/16" socket (with
wrench flats on the drive end or use adapter J-21501 and a
box wrench on the pulley retaining nut, insert a 5/16" alien
wrench through the socket and adapter into hex hole in the
shaft to hold the shaft while removing the nut.
11. Remove rotor and spacers from the drive end frame
assembly.
12. Remove drive end frame bearing retainer plate
screws, plate, gasket, bearing, and slinger from end frame (if
necessary).
C L E A N I N G A N D I N S P E C T I O N
W ith generator completely disassembled the
components should be cleaned and inspected. Be sure testing
equipm ent is in good working order before attem pting to
check the generator.
1. W ash all metal parts except stator and rotor
assemblies.
2. Clean bearings and inspect for sealing, pitting or
roughness.
3. Inspect rotor slip rings, they may be cleaned with 400
grain polishing cloth. R otate rotor for this operation to
prevent creating flat spots on slip rings.
4. Slip rings which are out of round may be trued in a
lathe to .002" maximum indicator reading. Remove only
enough m aterial to make the rings smooth and concentric.
Finish with 400 grain polishing cloth and blow dry.
5. Slip rings are not replaceable-excessive damage will
require rotor assembly replacement.
6. Inspect brushes for wear. If they are worn halfway,
replace. Inspect brush springs for distortion or weakening.
If brushes appear satisfactory and move freely in brush
holder, springs may be reused.
T E S T I N G
W here specified, conduct the following tests using an
ohm m eter with a 1-1/2 volt cell and use the lowest range
scale for the readings.
Rotor Field Winding Checks (Fig. 6D-10C)
The rotor may be checked electrically with a 110-volt
test lam p or an ohmmeter.
Open C irc u it
Connect one test lamp or ohmmeter lead to each slip
ring. If the lam p fails to light or if the ohm m eter reading is
high, the windings are open.
S h o rt C irc u it
The windings are checked for shorts by connecting a 12
volt battery and an am m eter in series with the two slip rings.
Note the am m eter reading. A n am m eter reading above the
specified field amperage draw indicates shorted windings.
Refer to Specifications at the end of this manual.
OHMMETER
(CHECK FOR SHORTS AND OPENS)