JLG 3246ES Service Manual - Manual (Page 72)

SECTION 3 - CHASSIS & SCISSOR ARMS
3-36 – JLG Lift – 3121166
3.7 DRIVE MOTOR ELECTRICAL EVALUATION
Several basic electrical tests can be performed on the
Drive Motors. Failure of one of these evaluations is sig-
nificant and may indicate that the device is physically
damaged.
Refer to Figure 7-2., Resistance Measurement. Discon-
nect the Main Battery Disconnect and all drive motor
cables during this analysis.
• Resistance < 2 Ohms Red to Black Armature Wires.
The heavy red and black conductors are connected
to the motor's armature winding. The winding is a
very low impedance and should appear to be a
short-circuit for an ordinary voltmeter. High resis-
tance can signal corrosion, improper crimps, dam-
aged cabling, worn brushes, a faulty commutator, or
an open armature winding.
• Resistance < 2 Ohms Blue to Orange Field Wires.
The blue and orange conductors are connected to
the motor's field winding. In order to make this mea-
surement, it will be necessary to disconnect the butt-
splice on the two orange wires or use a piercing
meter probe. As with the armature, the field is a very
low impedance and should appear to be a short-cir-
cuit for an ordinary voltmeter. High resistance can
signal corrosion, improper crimps, damaged connec-
tors, damaged cabling, or an open field winding.
• Resistance 15-25 Ohms Yellow to Brown Brake
Wires. The yellow and brown wires are connected to
the integral brake. Improper resistance can signal
corrosion, improper crimps, damaged cabling, or a
faulty solenoid.
• Resistance > 1 MegaOhms Red Armature Wire to
Motor Housing. The armature winding should be
electrically isolated from the motor housing. Low
resistance may be an indication of a crushed cable, a
burned cable, or a burned armature winding. Investi-
gate by disconnecting the drive motor cable from
the motor and re-measure resistance (isolation).
• Resistance > 1 MegaOhms Blue Field Wire to
Motor Housing. The field winding should also be
electrically isolated from the motor housing. Low
resistance may be an indication of a crushed cable, a
burned cable, or a burned field winding. Investigate
by disconnecting the drive motor cable from the
motor and re-measure resistance (isolation).
• Resistance > 1 MegaOhms Red Armature Wire to
Blue Field Wire. The armature and field windings
should also be electrically isolated from one another.
Low resistance may be an indication of a crushed
cable, a burned cable, damaged windings. Investi-
gate by disconnecting the drive motor cable from
the motor and re-measure resistance (isolation).
Servicing Guidelines
Since the operating environment of industrial equip-
ment varies widely, the following are suggested for peri-
odic maintenance inspection intervals.
• Normal Service – Perform routine inspection (out-
lined in the Inspection and Service portion of this
section) every 1,000 hours of drive time.
• Severe Service – Perform routine inspection every
500 hours of drive time. Severe service environments
are listed below:
a. Dusty or dirty locations like cement plants,
lumber and flour mills, coal mining, stone
quarries, etc.
b. High temperature areas like steel mills, found-
ries, etc.
c. Environments with sudden temperature
change, such as in refrigeration plant, etc.