JLG 3246ES Service Manual - Manual (Page 66)

SECTION 3 - CHASSIS & SCISSOR ARMS
3-30 – JLG Lift – 3121166
Inspection and Service
1. Carefully blow out any accumulated carbon dust
and dirt from the end head and the frame assem-
bly using clean, oil free, compressed air.
2. Replace brushes (3) that are worn below their
usable length (0600 in.), show signs of uneven
wear or signs of overheating, such as discolored
brush shunts and brush springs. Brushes should
always be replaced in complete sets of four or
eight. USe identical replacement parts; do not sub-
stitute brush grades as the brushes are matched to
the motor type and application to provide the best
service. Substituting brushes of the wrong grade
can cause premature failure and excessive brush
wear.
3. Make sure the brush box assembly (5) is tight on
the commutator end head. Replace brush box
assemblies in the commutator end head if they are
physically damaged or brush holders are loose on
the brush plate.
4. Visually inspect the frame and field assembly (1)
for overheating or other signs of damage. Check
all wiring to insure that the insulation is in good
condition. Verify that pole screws are torqued to
250-300 in-lb [28.2-33.9 N-m]. Verify field resis-
tance using a suitable ohmmeter per the appropri-
ate motor specification. Verify that the field is
electrically isolated from the frame using a dielec-
tric tester. Replace as necessary.
5. Visually inspect the armature (2) assembly for
signs of overheating or physical damage. Visually
inspect the seal surface of the shaft for excessive
wear. Check for grounded circuits using a dielec-
tric tester by applying voltage between the com-
mutator and the shaft. Visually inspect the
commutator for excessive wear and overheating.
Replace as necessary.
6. Visually inspect the brake surfaces for excessive
wear. Remove any RTV Silicone sealant that may
be present on the friction disc, cover, or commuta-
tor end head. Replace brake assembly (11) if nec-
essary.
7. Visually inspect the wire harness (8) for frayed
insulation, loose terminals, or other damage.
Replace as necessary.
Reassembly
1. After inspection and servicing, reassemble the wir-
ing in the commutator end head (9) as originally
found. Ensure the wiring does not contact metal
parts and that it allows the brushes to move unre-
stricted in the holders. Motor terminals must be
assembled as shown Figure 4. Torque bottom ter-
minal nut to 110-140 in-lb. (12.4-15.8 Nm).
2. After the motor has been disassembled, it is rec-
ommended that new bearings be installed
because bearings may have been damaged during
removal. Although the bearings may appear and
feel good, the bearing races could be “brinelled”
(races or balls deformed) and may exhibit noise
and vibration problems or fail within a relatively
short period of service. Press a new bearing into
the commutator end head, pressing on the outer
race only. See Figure 3. Replace the snap ring (6) in
the snap ring groove.
3. Press the armature (2) commutator end into the
commutator end head and bearing assembly,
carefully supporting the inner-race of the bearing.
See Figure 3.
4. Carefully release the brush springs (4) allowing the
brushes to contact the commutator. Make sure
1. Press Fixture must press against Outer Race
2. Bearing
3. End Head (held stationary)
4. Armature Assembly
5. Assembled End Head, Bearing, and Retaining Ring
6. Press Fixture must press against Inner Race (held station-
ary)
Figure 3-27. Bearing Pressure Guidelines