JLG M450 ANSI Service Manual - Manual (Page 56)

SECTION 3 - CHASSIS & TURNTABLE
3-16 – JLG Lift – 3121127
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.
Verification w/ Analyzer Procedure
Below is a procedure using the Analyzer that will verify
that the speed sensors are installed correctly.
THIS PROCEDURE REQUIRES A LARGE SPACE CLEAR OF
OBSTRUCTIONS. THE OPERATOR SHOULD BE FAMILIAR WITH
JLG EQUIPMENT AND BE PREPARED TO USE THE FOOTSWITCH
TO STOP THE MACHINE. READ AND UNDERSTAND THIS ENTIRE
PROCEDURE PRIOR TO BEGINNING.
1. Before beginning this procedure, insure that there is
at least 10 ft (3m)in front and back of machine. Be
sure that all other personnel stand clear of the
machine during this procedure.
2. Unplug the left speed sensor from the posi-trac tilt
module.
3. Power up the machine in platform mode and plug in
the Analyzer in the platform.
4. Use the right and left cursor keys on the analyzer to
highlight "DIAGNOSTICS" and press enter.
5. Use the right and left cursor keys on the analyzer to
highlight "DRIVE" and press enter.
6. Use the right and left cursor keys to display ’SPEED
0%" on the analyzer.
7. While watching the analyzer display, select drive for-
ward. Be ready to remove your foot from the foot-
switch if the machine lunges forward.
8. The analyzer display should read the following if the
RIGHT speed sensor is adjusted properly: "SPEED
20% FWD".
9. If the speed sensor is adjusted improperly, the ana-
lyzer will display "SPEED 20%REV" and the machine
will lunge forward.
10. Adjust the right speed sensor using the preceding
Adjustment Procedure until the analyzer displays
"SPEED 20% FWD" when forward is selected at the
platform. The percentage displayed is not critical,
just the direction.
11. After obtaining the display in step 10, operate the
machine in both forward and reverse directions. The
machine should be controllable in both directions
and will only drive at a maximum of creep speed.
The display on the analyzer should match the direc-
tion selected.
12. After completing adjustment of the right sensor, plug
the left sensor into the posi-tilt module.
13. Unplug the right sensor from the power module.
14. Power up the machine in platform mode and plug in
the analyzer in the platform.
15. Use the right left cursor keys on the analyzer to high-
light diagnostics and press enter.
16. Use the right and left cursor keys on the analyzer to
highlight drive and press enter.
17. Use the right and left cursor keys to display "speed
0%" ON THE ANALYZER.