Pontiac tempest 1968 Service Manual page 352

E N G I N E E L E C T R I C A L
6E-3
SERVICE
ARMATURE
W PIPE
. COUPLING
If the armature commutator Is worn, dirty, out of
round or has high insulation, the armature should
be put In a lathe so the commutator can be turned
down. The insulation should then be undercut 1/32"
wide and 1/32" deep, and the slots cleaned out to re­
move any trace of dirt or copper dust. As a final
step in this procedure, the commutator should be
sanded lightly with No. 00 sandpaper to remove any
burrs left as a result of the undercutting procedure.
The armature should be checked for opens, short
circuits and grounds as follows:
F i g . 6E-2 Driving Retainer Off Snap Ring
CLEAN AND INSPECT
1. Test overrunning clutch action. The pinion
should turn freely in the overrunning direction.
Check pinion teeth to see that they have not been
chipped, cracked, or excessively worn. Replace as­
sembly if necessary. Badly chipped pinion teeth may
indicate chipped teeth on the ring gear. This should
be checked under such conditions and replaced if
necessary.
2. Inspect brushes for wear. Replace if worn to
one-half their original length. Check brush holders
to see that they are not deformed or bent, but will
properly hold brushes against the commutator.
3. Check fit of armature shaft in bushing of drive
housing. Shaft should fit snugly in the bushing. If the
bushing is worn, it should be replaced.
4. The overrunning clutch, armature and fields
should not be cleaned in any degreasing tank, or with
grease-dissolving solvents, since these would dis­
solve the lubricants in the clutch mechanism and
would damage the insulation in the armature and
field coils. It is suggested that all parts except the
clutch, be cleaned with oleum spirits and a brush.
The clutch can be wiped with a clean cloth.
If the commutator is dirty it may be cleaned with
No. 00 sandpaper. Never use emery cloth to clean
commutator.
1. Open— The most likely place for an open to
occur is at the commutator riser bars as a result of
excessively long cranking periods. Inspect the points
where the conductors are joined to the commutator
bars for loose connections. The poor connections
cause arcing and burning of the commutator bars as
the starting motor is used. If the bars are not too
badly burned, repair can often be effected by re-
soldering the leads in the riser bars (using rosin
flux), and turning down the commutator in a lathe to
remove the burned material. The insulation should
then be undercut.
2. Short Circuit—Short circuits in the armature
are located by use of a growler. When the armature
is rotated in the growler with a steel grip such as a
hacksaw blade held above it, the blade will vibrate
above the area of the armature core in which the
short circuit is located. Shorts between bars are
sometimes produced by brush dust or copper be­
tween the bars. These shorts can be eliminated by
cleaning out the slots.
3. Ground— Grounds in the armature can be de­
tected by the use of 110-volt test lamp and test
points. If the lamp lights when one test point is
placed on the commutator with the other point on
the core or shaft (Fig. 6E-3), the armature is
grounded. Grounds occur as a result of insulation
failure which is often brought about by overheating
of the starting motor produced by excessive long
cranking periods or by accumulation of brush dust
between the commutator bars and the steel commu­
tator ring.
FRAME AND F I E L D
The field winding can be checked for an open or a
ground by using a test lamp as follows:
1. Using a 110-volt test lamp, place one lead on
each end of the field coils connected in series (Fig.
6E-4). If lamp does not light, the field coils are
open and must be repaired or replaced.