Checking the Operation of the Interlock Switches
(continued)
• Prevents the machine 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.
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.
1. 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).
2. Tests 5-9 test the ‘Engine Run’ function. For each test, start the power unit so
that the engine is running. 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 should continue running or
stop running as described for each test.
4520P Page 6–7 Electrical System: Electrical System Quick Checks
09.40003Rev 00
To Next Page
