Service Manual

11. Put the armature on a growler tester to check for a
shorted armature. A burned commutator bar is an indi-
cation of a shorted armature. With the growler turned
on, put a thin strip of steel or a hacksaw blade on the
armature as it is slowly rotated. If the metal strip vibrates
over a winding, that winding is short circuited. Short
circuited windings are sometimes caused by metal in
the commutator bridging the gap from on commutator
bar to the next. By removing the bridged metal, this
condition can be corrected. If this does not correct the
short replace the armature.
12. Measure the commutator O.D. and depth of under-
cut
. Repair or replace if the service limit is exceeded.
Check the commutator outside surface for dirt and
roughness. If rough, polish the commutator with fine (00
or 000) sandpaper. DO NOT use emery cloth.
Item Standard Service Limit
Commutator O.D. 38.7 mm (1.52 in.) – 1.0 mm (– 0.4 in.)
Depth
of Undercut 0.5 mm (0.02 in.) 0.2 mm (0.008 in.)
13. Check the brushes. Replace if worn beyond the
service limit. Check the brush spring tension. Replace
the springs if tension is less than the service limit. Check
for insulation between the positive brush holder and
holder base. If poorly insulated, replace the holder
assembly. Check the brush holders for proper staking.
Item Standard Service Limit
Height of Brush 17 mm (0.67 in.) 6 mm (0.24 in.)
Spring Pressure 3 kg (6.6 lb.)
14. Check for continuity between one end of field coil
(brush) and yoke. There should be no continuity. Check
for continuity between both ends of coil (brushes). There
should be continuity if the field coil is good. Check the
poles and coil for tightness.
Figure 49
Figure 50
Liquid Cooled
Diesel Engine
Figure 51
Workman 3300-D/4300-D
P
age 4 - 39 Liquid Cooled Diesel Engine