Armature; Frame And Field; Testing Armature For Ground - Pontiac Grand Prix Service Manual

ENGINE ELECTRICAL
6E-3
b. Slide a standard half-inch pipe coupling or other
metal cylinder of suitable sue (an old pinion of
suitable size can be used if available) onto shaft so end
of coupling or cylinder butts against edge of retainer
(Fig. 6E-2). Tap end of coupling with hammer, driving
retainer towards armature and off snap ring.
c. Remove snap ring from groove in shaft, using pliers
or other suitable tool. If snap ring is too badly
distorted during removal, it will be necessary to use a
new one when reassembling clutch.
d. Slide retainer and clutch from armature shaft.
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 assembly 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 tit 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 dissolve 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.
SERVICE
ARMATURE
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.
Tht starter motor commutator in all 1969 model cars is
of the molded type and should not be undercut, since
undercutting will reduce the bonding of the molding
material. When turning the modled commutator, only
a very light clean-up cut should be made. The
minimum diameter of the commutator after turninn
should not be less than 1.650 inches. As a final step
tbis 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:
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 resoldering the leads in the riser
bars (using rosin flux), and turning down the commuta-
tor in a lathe to remove the burned material.
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 ln which the short
circuit is located. Shorts between bars are sometimes
produced by brush dust or copper between the bars.
These shorts can be eleminated by cleaning out the
slots.
0
3. Ground
-
Grounds in the armature can be detected
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 commutator ring.
FRAME
AND FIELD
The field winding can be checked for an open or a
ground by using a test lamp as follows:
1. Uskg a 110-volt test lamp, place one lead on each
Fig. 6E-3 Testing Armature For Ground