Service Brake Switch - JLG sky trak mmv Service Manual

10.13.6

Service Brake Switch

The service brake switch (8) is located next to the service
brake pedal (9) and attached to a cab weldment (10) and
connected to a wiring harness lead (11). Two screws
(12), flat washers (13) pass through the weldment (10)
and service brake switch (8) and are secured with two flat
washers (14) and elastic locknuts (15). The weldment
has a machined slot (16) which allows adjustment of the
proximity switch.
8
15
11
14
13
10
The service brake switch (8) is a proximity type switch
that is normally in a closed position until the brake pedal
(9) is pressed and the brake pedal arm (17) begins to
move through its arc. The proximity sensor detects the
brake pedal arm metal and opens the circuit. The service
brake switch circuit is also spliced into the Stabil-TRAK
circuit through the dash panel logic. (Refer to Section
10.9.8, Stabil-TRAK Indicator Troubleshooting .)
a. Service Brake Switch Removal
If the service brake switch (8) is suspect, remove the
switch. Remove the two screws holding the switch. Dis-
connect the switch from the cab harness (11) and remove
from vehicle. Test the switch for continuity and shorting.
Replace a defective or faulty switch.
b. Service Brake Switch Installation and
Adjustment
Note: The service brake switch adjustment will require
two people. Enlist the help of an assistant before
attempting follow the adjustment procedure.
1. When installing the service brake switch (8), make
sure that the switch face is parallel with the brake
pedal arm (17) and is no more then 1/4" (6,35 mm)
from the brake pedal arm.
2. Leave the two screws (12), attaching the brake
switch to the cab structure (10), just loose enough to
adjust the brake switch.
Model MMV Rev. 12/04
16
9
17
12
WARNING:
adjust the service brake switch without an
assistant. Anytime the engine is running and
the parking brake is disengaged, there must be
an operator located in the cab and the two
front tires must be blocked. Death or serious
MT0850
personal injury could result from the vehicle
lurching forward or backward and running over
the person attempting to adjust the service
brake switch.
3. Connect a 1000 psi (69 bar) pressure gauge to the
test port (18) closest to the mounting plate (19) on
the service brake valve (20).
4. Start the engine and run it at low idle.
5. Depress and hold the brake pedal to maintain
150 psi (10,3 bar) brake pressure.
6. Position the brake switch so the brake lights come on
at the 150 psi (10,3 bar) brake pressure.
7. Tighten the two attaching screws (12).
8. Block both front tires, position the boom above 40°,
have the engine running at idle, the transmission in
forward 4th gear and the park brake released. Slowly
depress the brake pedal. The Stabil-TRAK dash light
must come on with a service brake pressure of
150 ±15 psi (10,3 ±1 bar). Re-adjust the brake
switch position as required to achieve the required
pressure.
9. Remove the pressure gauge.
In order to test the switch for proper operation, the boom
must be raised above the 40° position, the parking brake
switch must be in the OFF position and the vehicle must
be in a forward or reverse gear mode. Proper operation
of the switch will activate the Stabil-TRAK dash panel
indicator. If the Stabil-TRAK indicator does not activate
when all conditions are met, the sensor must be adjusted.
Electrical System
20
19
18
NEVER attempt to
MM5450
10.143