Onan MEP-003A - Page 55

TM5-6115-585-34
NAVFAC P - 8-262-12
TO - 35C2-3-455-2
TM - 05684C - 34
( 6 ) Armature . Inspect armature ( 27 , figure 5-1 )
for wear . Inspect commutator for wear . Turn com
mutator surfaces
on a lathe to
remove grooves
and
out - of -
round
.
Replace
if
excessively
worn .
( 7 ) Yoke . Inspect yoke ( 26 ) for damage or wear .
( 8 ) Frame Assembly . Inspect frame assembly ( 19 )
for damage . Check wires of field coil for burning or
worn insulation . Check pole shoes for tightness . Check
field coils for signs of armature contact which in
dicates bad bearings . Repair or replace if defective .
e
.
Test
Bench
.
( 1 ) Testing Starter . Refer to Operator and
Organizational Maintenance Manual .
(
2
)
Testing
Armature
.
( a ) Testing Armature for Grounds . Touch ar
mature shaft and the end of each commutator bar with
a pair of ohmmeter leads . There should be no con
tinuity . If continuity is indicated between any commu
tator bar and shaft , it indicates a grounded armature .
Replace a grounded armature . See figure 5-3 .
( b ) Testing Armature for Shorted Coils . A
growler is necessary to test for shorted coils . With
the armature in the growler turn the growler on and
1. Armature
2. Growler
3. Hack - saw blade
TS 6115-585-34 / 5-4
Figure
5-4
.
Testing
Armature
for
Shorted
Coils
run
a
steel
strip
over
the
armature
surfaces
.
If
a
coil
is
shorted
,
the
steel
strip
will
become
magnet
ized
and
vibrate
.
Rotate
the
armature
slightly
and
repeat
the
test
.
Do
this
for
one
complete
revolution
of
the
armature
.
See
figure
5-4
.
If
the
armature
has
a
short
or
ground
,
replace
it
.
( c ) Testing
Armature
for
Open
Coils
. Test
coils
for
continuity
with
ohmmeter
. High
resistance
reading
indicates
open
coil
.
( d ) Testing Commutator Runout . Place arma
ture in a test bench and check runout with a dial in
dicator . See figure 5-5 . When commutator runout ex
ceeds .004 " , commutator should be refaced . After
refacing commutator , check that it meets minimum
specifications . Check and , if necessary , undercut
mica as given under repair .
(
e
)
Testing
Armature
Shaft
Runout
.
Place
ar
mature
in
a
test
bench
and
check
shaft
runout
with
a
dial
indicator
.
See
figure
5-6
.
If
the
shaft
is
bent
or
worn
armature
must
be
replaced
.
Should
not
exceed
0.006
inch
.
1. Armature
2. Ohmmeter
TS
6115-685-34
/
5-3
Figure
5-3
.
Testing
Armature
for
Grounds
( 3 )
Testing
Field
Coils
.
See
Operator
and
Organizational
Maintenance
Manual
.
5-4