JLG E300 Service Manual - Manual (Page 57)

SECTION 3 - CHASSIS & TURNTABLE
3121253 – JLG Lift – 3-23
3.5 SPEED SENSOR ADJUSTMENT
FOR PROPER DRIVE OPERATION, THE SPEED SENSORS (2)
MUST BE PROPERLY INSTALLED AND ADJUSTED. THE SENSOR
OPERATES ON A LEADING PULSE TO SHOW DIRECTION. IF
INSTALLED INCORRECTLY, THE SENSOR WILL NOT BE ABLE TO
SENSE THE PROPER DIRECTION. IF BOTH SENSORS ARE
INSTALLED INCORRECTLY, THE JLG CONTROL SYSTEM WILL
THINK THE MACHINE IS ON A HILL AND THE MACHINE WILL GO
INTO FULL SPEED MODE IMMEDIATELY. IF ONLY ONE SENSOR IS
INSTALLED WRONG, THE CONTROLLER SENSES A PROBLEM
AND THE MACHINE WILL ONLY DRIVE AT CREEP SPEED. IF BOTH
SENSORS ARE ADJUSTED TOO FAR OUT, THE CONTROL SYSTEM
WILL NOT DRIVE THE MACHINE.
Adjustment Procedure
1. Back off the locking nut and o-ring.
2. Thread the sensor in until it bottoms out. (do not
force).
NOTE: There are two notches on each speed sensor.
3. Back-off 3/4 to 1 turn and align the notches accord-
ing to the inside notch on each speed sensor. If
there are no notches, align the speed sensor wires
as shown in Figure 3-16., Speed Sensor Orientation.
4. Use a 1/2” wrench to hold the sensor and a 11/16”
wrench to snug the lock nut to the brake.
Speed Sensor Installation Verification
The motor controller averages the readings from the right
and left speed sensors and therefore, it can be difficult to
detect if the speed sensors are adjusted properly. When
the positrac keeps coming in and out while on level sur-
faces, this is a sure indication that one of the speed sen-
sors is not adjusted properly.
The worse case condition of speed sensor misadjustment
occurs when both sensors are installed in a manner that
allows them to indicate the exact opposite direction that
the machine is traveling. This situation causes the control-
ler to believe that the machine is rolling in opposite direc-
tion than that selected by the operator. The controllers
reaction to this situation is to put more power into the
drive motors to attempt to overcome the fact that it
believes the machine is rolling backwards. This presents
itself as uncontrolled movement in the direction selected
by the operator until the controller recognizes that it is
placing maximum power in the motors and the controller
and the speed sensors are still reporting movement in the
opposite direction. The controller responds by shutting
down drive and reporting flash code 5/5- Vehicle Runaway
Check Speed Encoders.
If either speed sensor is disconnected or faulty, the con-
troller will recognize this condition and immediately report
flash code 5/5 - Left or Right speed Encoder Faulty.