Yale MPB040E Manual page 101

0620 YRM 0294
4. Remove and inspect brushes for damage or un-
even wear. Replace all brushes if any brush is
worn or damaged. The brushes must be at least
half their original length. Move brush springs
away from top of each brush and pull brushes
from their holders to inspect surface that rides on
commutator. See Figure 3. That surface must
have the same shape as the commutator and
must not have cracks or defects. Some brushes
have wear sensor wires attached, even if they are
not connected to an indicator. Replace these
brushes if brushes are worn enough to see sen-
sor at commutator end of brush.
5. Inspect commutator surface. See Table 1 and Ta-
ble 2. Carefully rotate armature. DO NOT damage
commutator if you use a tool to rotate armature.
The commutator wears slowly in normal service.
The mica must be cut below the surface of the
commutator bars after a long service period or after
a commutator has been turned in a lathe.
A commutator that has been in service will have a
smooth and polished surface with a darker brown
color where it rotates under the brushes. A varia-
tion of color on the commutator surface between
light brown and darker brown is normal. The sur-
face condition is the lubrication between the com-
mutator and the brushes. The brushes will wear
rapidly if this surface condition does not develop
during the first 6 to 10 hours of operation after a
commutator with a new surface is installed. If the
commutator has deep grooves, rough edges of the
bars, or a few bars that are black or raised above
the others, the motor must be removed for service.
6. Inspect white or gray insulation (mica) between
commutator bars. The mica must not touch the
brushes or the brushes will wear very rapidly.
7. To replace a brush set, remove screw that holds
brush wires to bus. Pull brush end of springs from
brushes, and pull brushes from holders. Lift brush
Brush and Commutator Inspection
springs away from holders, and install new
brushes so brush commutator surface fully
touches commutator. Make sure the springs are
pushing on each brush. Install and tighten screws
for brush wires and bus connectors.
8. Carefully install brush covers so sparks are kept
inside motor housing. Install battery as described
in Operating Manual or the Periodic Mainte-
nanceYRM section for your lift truck.
1. BRUSH
2. BRUSH SPRING
Figure 3. Brush Removal and Inspection
3. MICA
3