SAFETY
Safety - 16
Operator Safety Interlock System
The 4520 power unit is equipped with a safety interlock system. This system:
• Prevents the engine from starting unless the parking brake is engaged and the SDLA control is in neutral.
• Prevents the PTO from starting if the operator is not in the seat.
• Prevents the power unit from driving if the parking brake is engaged.*
•
Shuts off the PTO if the operator leaves the seat.
•
Shuts off the engine (and fuel pump) if the operator leaves the seat without engaging the parking brake.
•
Shuts off the engine if the forward / reverse controls (SDLA lever or foot pedal) are moved from neutral
while the parking brake is engaged.
* The parking brake must be completely disengaged before moving the SDLA lever forward or backward or the power unit engine will shut off.
Testing the Safety Interlock System
WARNING
Never operate the power unit if the safety interlock
system is malfunctioning. Do not disengage or by-
pass any switch. Failure to heed this warning could
result in injury to yourself or others, or damage to
property.
WARNING
The parking brake must be disengaged during por-
tions of the safety interlock system test. Place wheel
chocks in front and back of the wheels to prevent
the power unit from moving.
CAUTION
The daily inspection should be performed prior to
initial startup for the day.
Perform the following safety interlock tests daily to test the electrical portion of the interlock system. Before
testing, park the power unit on a level surface, place wheel chocks in front and back of the wheels, and place
the high/low range shift lever in the neutral position. After testing is complete, place the high/low shift lever in
either high or low range, engage the parking brake, and remove the wheel chocks.
Tests 1-4
test the ‘Engine Start’ function. For each test, turn the ignition key to the RUN position (do not start
the engine). As listed for each test, engage or disengage the parking brake*, place the SDLA in neutral or out of
neutral^, and sit on the seat or raise your body weight from the seat. The engine starter should or should not
engage as described for each test.
Engine
Start
Test
Number
Parking Brake*
Engaged
Forward/Reverse Control
(SDLA) in Neutral^
Operator Present in Seat
Engine Starts
1
No
Yes
Yes
No
2
Yes
No
Yes
No
3
Yes
Yes
No
Yes
4
Yes
Yes
Yes
Yes
* This tests the function of the parking brake switch. The parking brake handle should be engaged the minimum amount necessary to activate the parking
brake indicator light on the information gauge.
^ This tests the function of the neutral switch located on the hydraulic pump. Depending on settings and the age of the power unit, the range for neutral for
the SDLA control may vary. For this test, the SDLA lever should move 2.5 cm (1 inch) or less forward or backward for neutral switch activation (measured at
the top of the lever).
https://www.tractormanualpdf.info/
