GMC PD-4103 Maintenance Manual page 133

GM COACH MAINTENANCE MANUAL
Sec. 7
Page 125
Make sure bearing inner races are in place on
drive end of armature shaft; then install drive
end frame assembly over shaft and races. Install
oil slinger and external toothed gear on armature
shaft and secure with washer and nut. Tighten
nut to 180 foot-pounds torque. Install baffle in
counterbore in drive end frame. Remove arma-
mre and drive end frame assembly from vise.
4. Mount field frame assembly in vise. Do
not tighten vise jaws sufficiently to distort frame.
Insert armature into field frame and position drive
end frame against field frame. Attach end frame
to field frame with ten cap screws, using lock
clip and washer under each cap screw head.
5. Slide ball bearing retainer plate over com-
mutator end of armature shaft. Install commutator
end frame assembly over armature shaft and po-
sition against field frame. Attach end frame to
field frame with six cap screws, using lock clip
and washer under each cap screw head. Tighten
screws only finger tight.
6. Install washer, nut, and cotter pin on com-
mutator end of armature shaft. Position commu-
tator end bearing outer retainer plate on end
frame, with new gasket between plate and end
frame. Insert screws through retainer plate and
end frame, then reach through openings in end
frame to position bearing inner retainer plate so
screws can be threaded into tapped holes in plate.
Tighten screws firmly.
7. Install brushes in holders and connect brush
leads, making sure connections are tight. Connect
lead from "A" terminal to insulated brush holder
connector.
8. Install air strainer and cover on commu-
tator end frame and attach with four thumb nuts.
9. Before installing generator on vehicle, ad-
just neutral point as described below; then test
as previously directed.
GENERATOR
NEUTRAL POINT ADJUSTMENT
Whenever generator has been disassembled,
new brushes, armature, or field coils installed,
the neutral point must be adjusted. The neutral
point refers to a particular relationship between
the field poles, armature windings, and brushes.
When the relationship of these parts is correct,
minimum arcing and best commutation and brush
life will be obtained. All brushes must be prop-
erly seated with a brush seating hone before ad-
justing neutral point.
CAUTION: Adjustment for neutral point
must be made as quickly as possible since
armature will begin to heat. Do not allow
armature to overheat. Adjust as follows:
1. With generator assembled and commutator
end frame attaching screws just tight enough to
hold end frame in place, place generator on test
bench with armature free to rotate, and without
any connection to generator field (F) terminal.
2. Connect a battery between generator arma-
ture (A) terminal and ground, and allow a current
of approximately 100 amperes to flow through
armature. (Current may be controlled by variable
resistance or by varying the number of battery
cells used.)
3. Note tendency of armature to rotate. The
neutral point is found by shifting (rotating) com-
mutator end frame into the position at which there
is no tendency for the armature to turn in either
direction. After this position has been found, ad-
vance brushes 1/2 to 3/4 the width of a commu-
tator bar, by rotating commutator end frame in
the direction of normal armature rotation. Tighten
commutator end frame attaching cap screws firmly
and secure with lock clips.