Electrical System Components; Warning Devices; Warning Indicator Lights - JLG sky trak mmv Service Manual

Electrical System
10.12 ELECTRICAL SYSTEM
COMPONENTS
Electrical components include warning devices such as
the indicators in the operator's display panel, horn, back-
up alarm, and other components such as the joystick, log-
ic panel, various solenoids and all accessories.
Examine the appropriate wiring diagrams and schematics
earlier in this section to help understand the wiring cir-
cuits involved.
10.12.1

Warning Devices

Vehicle warning devices include the horn, instrument
panel warning lights, and the back-up alarm.
a. Horn
The horn (1) is mounted forward of the cab on the vehicle
frame.
The horn sounds when the momentary-contact horn but-
ton on the center of the steering wheel is pressed. When
the blackout light system is activated the horn will not op-
erate. Removal of the horn button is discussed in Section
3.5.1, a. Steering Wheel Removal of this manual.
The horn sound is produced by a solenoid-actuated dia-
phragm in the horn that develops a resonating air column
in the horn trumpet, which is shaped to project the sound.
If the horn doesn't sound when the horn button is
pressed, check that the fuse is not blown.
Check for corrosion on the horn mounting that may be
preventing a solid ground, and check for a loose horn
wire. Test the horn switch for continuity when the horn
button is pressed.
If the problem is still not located, remove the horn from
the frame and test it using short, heavy-gauge wires con-
nected to a fused or otherwise protected 6-amp minimum
output, 12-volt DC power supply.
10.108
10.12.2

Warning Indicator Lights

There are eight subdued or "hidden" warning indicator
lights present in the operator's display panel
(2 through 8). These warning indicators illuminate during
critical circumstances.
IMPORTANT: All eight warning indicator lights demand
immediate attention and vehicle service. In many cases,
the vehicle should be shut down as soon as practical to
help prevent serious mechanical failure. Appropriate ser-
vice procedures for each circuit, as applicable, appear
elsewhere in this section of the manual.
a. Engine Coolant Temperature Warning Indicator
This indicator (2) is illuminated when the engine
coolant temperature is above 210° F (99° C).
1
An audible alarm will sound, and the engine
MT3440
must be shut down as soon as practical to help
avoid engine damage. For additional information refer to
Section 10.9.1, Engine Coolant Temperature Warning In-
MT3690 dicator Troubleshooting .
b. Transmission Temperature Warning Indicator
This indicator (3) illuminates when the transmis-
sion fluid temperature exceeds 250° F (121° C).
An audible alarm will also sound, and the vehi-
MT3450
cle should be stopped and the engine allowed
to run at high idle for five minutes. If the light and alarm
DO NOT cease after five minutes, the engine must be
shut down to help avoid transmission damage. For addi-
tional information refer to Section 10.9.2, Transmission
Temperature Warning Indicator Troubleshooting .
4
8
3
6 5
7 2
Model MMV Rev. 12-04
MM1981