commutator to give proper performance. Check by
which is often brought about by overheating of
hand to insure that the brush springs are giving
t h e cranking motor produced by excessively
firm contact between the brushes and commutator
l o n g cranking periods or by accumulation of
I f the springs are distorted or discolored, they
b r u c h dust between the commutator bars and
should be replaced.
the steel commutator ring.
FIELD COIL CHECKS
ARMATURE SERVICING
The circuits used is shown in the wiring diagrams
If the armature commutator is worn. dirty, out of
o f Figure 5 The field coils can be checked for
round, or has high insulation. the armature should
grounds and opens by using a test lamp
be put in a lathe so the commutator can be turned
Grounds-If the motor has one or more coils nor-
down. The insulation should then be undercut 1/32
mally connected to ground. the ground connections
of an inch wide and 1/32 of an inch deep, and the
must be connected during this check Connect one
slots cleaned out to remove any trace of dirt or copper
lead of the 110-volt test lamp to the field frame and
dust. As a final step in this procedure. the commuta-
the other lead to the field connector If the lamp
tor should be sanded lightly with No 00 sandpaper
lights at least one field coil is grounded which must
to remove any burrs left as a result of the undercut-
ting procedure NOTE: The undercut operation must
be repaired or replaced This check cannot be made
if the ground connection cannot be disconnected
be omitted on cranking motors having Test Speci-
fications 2412, 2415, 3501, 3564 and 3574 as listed
Opens-Connected test lamp leads to ends of field
in Delco-Remy Service Bulletins 1M-186 and 1M-187
coils If lamp does not light. the field coils are open
Do not undercut commutators on motors having
these specifications
The armature should be checked for opens. short
circuits and grounds as follows
1. Opens--Opens are usually caused by excessive-
ly long cranking periods The most likely place
for an open to occur IS at the commutator riser
bars Inspect the points where the conductors
are joined to the commutator bars for loose con-
n e c t i o n s Poor connections cause arcing and
burning of the commutator bars as the cranking
m o t o r I S used. If the bars are not too badly
burned, repair can often be effected by resolder-
ing or welding the leads in the riser bars (using
rosin flux), and turning down the commutator in
Figure 5
a lathe to remove the burned material The in-
s u l a t i o n should then be under cut except as
noted above
FIELD COIL REMOVAL
2 . Short Circuits-Short circuits in the armature
Field coils can be removed from the field frame
are located by use of a growler When the arma-
assembly by using a pole shoe screwdriver A pole
ture IS revolved in the growler with a steel strip
shoe spreader should also be used to prevent distor-
such as a hacksaw blade held above it the blade
tion of the field frame Careful installation of the field
will vibrate above the areas of the area of the ar-
coils is necessary to prevent shorting or grounding
mature core in which the short circuit IS located
of the field coils as the pole shoes are tightened into
S h o r t s between bars are sometimes produced
place Where the pole shoe has a long lip on one side
by brush dust or copper between the bars These
and a short lip on the other the long lip should be
s h o r t s can be eliminated by cleaning out the
assembled in the direction of armature rotation so it
slots
becomes the trailing (not leading) edge of the pole
3. Grounds-Grounds in the armature can be de-
shoe
tected by the use of a 110-volt test lamp and test
points If the lamp lights when one test point is
C L U T C H ASSEMBLY
placed on the commutator with the other point
The Positork drive is serviced by complete re-
on the core or shaft. the armature IS grounded
placement only
Grounds occur as a result of insulation failure
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