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GM COACH MAINTENANCE MANUAL
Sec. 7
Page 119
2.
Mark commutator end frame, field frame,
center bearing plate, and drive housing to facili-
tate reassembling in correct position.
3.
Remove cover band and disconnect the two
field winding leads from brush holders.
4.
Remove cap screws and lock clips attach-
ing commutator end frame to field frame.
Remove
commutator end frame assembly.
5.
Remove cap screws and lock clips attach-
ing drive housing to field frame.
Remove field
frame from armature and drive housing.
6.
Remove shift lever cover attaching screws.
Remove cover, shift lever assembly, and shift
lever spring.
Remove drive housing from arma-
ture shaft.
7.
Remove cotter pin attaching pinion stop to
armature shaft, then remove stop.
Remove Dyer
Drive assembly from armature shaft, noting posi-
tion of parts to aid in reassembly.
Remove two
washers, center bearing plate, and collar from
armature shaft.
INSPECTION, TESTS, AND REPAIR
Wash all parts except field frame and field
coil assembly, armature, and overrunning clutch
in cleaning solvent.
Armature, clutch, and field
coils should be wiped clean with a dry rag. Tests
described below may be made on a conventional
growler equipped with test lamp and prods.
ARMATURE
Check armature to commutator leads to make
sure they are properly soldered.
Place one prod
of test lamp on armature and other on commutator.
If test lamp lights,
armature is grounded and
should be replaced if defect is not readily appar-
ent and reparable.
Place armature on growler.
Hold
hacksaw
blade over armature and slowly rotate armature.
If saw blade vibrates, armature is short circuited.
Before replacing, inspect commutator slots for
copper or brush dust deposits.
Clean thoroughly
and retest.
Bruned commutator riser bars are sometimes
caused by an open-circuited armature.
If bars
are not too badly burned, armature can sometimes
be repaired by resoldering the leads in riser bar,
using rosin flux solder.
After soldering, turn
down commutator and undercut the mica.
COMMUTATOR
Inspect commutator and if found to be rough,
out-of-round, worn or has high mica, filled slots,
or is burned, repair as follows:
Turning Down
Place armature in lathe and turn down com-
mutator to remove worn spots, out-of-round, or
STARTING SYSTEM
rough condition. Do not cut deeper than necessary
to clean up.
Undercut Mica
Mica between commutator segments must be
below edges of segments.
Start groove with a
small three-cornered file; then use a hacksaw
blade to undercut mica to a depth of 1/32".
Use
No. 00 sandpaper to clean and smooth up com-
mutator, then blow all dust and cuttings out of
grooves.
FIELD COILS
Place one test prod on field frame and touch
other prod to each of the field coil leads which
connect to the brush holder. The test lamp should
light when each circuit is completed. If lamp does
not light, field circuit is open. Inspect connections
between coils.
Disconnect field coil leads from field frame
at drive end. Pry leads away from frame to elim-
inate electrical contact.
Place one test prod on
field frame and other on each of the exposed leads.
Lamp should not light.
If lamp does light, field
coils are grounded and must be replaced.
COMMUTATOR END FRAME
Remove all brushes.
Place one test prod on
end frame and other on brush holder and on ter-
minal stud.
Test lamp should not light. If test
lamp does light,
it
is an indication of defective
brush holder insulation or terminal insulators.
Replace defective insulation under brush holders
or at terminal.
If brushes are worn down to less than one-
half their original length, they must be replaced.
Be sure leads are secure in brushes and that
clips are properly soldered to leads.
Check brush spring tension. If not within lim-
its listed in "Specifications" at end of this group,
replace with new springs. Examine hinge pins and
brush holders for bent or damaged condition. Any
condition which might prohibit free brush action
must be corrected.
Replace end frame bushing if worn excessively
or out-of-round.
DRIVE HOUSING
Replace bushing in drive housing if worn ex-
cessively or out-of-round.
Also replace oil wick
at bushing.
CENTER BEARING
If bushing in center bearing plate is worn ex-
cessively or out-of-round, replace.
Also replace
oil wi.ck in center bearing plate.
DYER DRIVE
Carefully inspect all parts of Dyer Drive for
wear or other damage. Check spring for weak or
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