GMC 1976 ZEO 6083 Maintenance Manual page 714

Figure 66-Testing Commutator Runout
OPEN ARMATURE : The most likely place to
check for an open circuit is at the commutator riser
bars . Inspect for loose connections on points where
the conductors are joined to the commutator bars.
COMMUTATOR RUNOUT : Place armature in
a pair of v-blocks and measure runout with a dial
indicator refer to Figure 66 . Measure both shaft and
commutator. A bent shaft requires replacement of
armature. When runout exceeds a .004 inch, com-
mutator should be refaced. Remove only enough
metal to provide a smooth, even surface.
OPEN FIELD COIL : Use a 120 volt test lamp
set for this test . Connect one probe of test lamp to the
yoke and the other probe to insulated brush. If lamp
does not light, the field coil is open .
NOTE :
This starter is compound wound, having
a series coil and a shunt coil. The grounded end
of the shunt coil is soldered inside of the yoke .
GROUNDED FIELD COIL : Use a 120 volt test
lamp set for testing for a grounded field coil. First
Figure 67-Testing Field Coil
ONAN MOTOR GENERATOR
24C- 3 7
Figure 68-Brush Replacement
disconnect the grounded end of shunt coil as shown
in Figure 67. Then connect one probe of test lamp to
yoke and the other probe to field coil connector lead .
If lamp lights, field coil is grounded .
BRUSH REPLACEMENT: Brushes that are
worn out to the wear limit line should be replaced as
shown in Figure 68. Brushes can be replaced after
removing the rear bracket.
When resoldering the brushes, make a low resist-
ance connection, using a high temperature solder
and resin flux.
BRUSH SPRINGS: The spring tension should
be taken using a push-type spring scale until the top
of a new brush protrudes 1/16 inch from the brush
holder . Spring tension should be 36 to 48 ounces on
the 4KW and 49 to 59 ounces on the 6KW (See
figure 69).
OVERRUNNING CLUTCH : The pinion gear
should rotate smoothly in one direction (not neces-
sarily easily), but should not rotate in opposite direc
tion. If pinion gear does not function properly, or if
pinion gear is worn or burred, replace the overrun-
ning clutch .
Figure 69-Testing Brush Spring Tension