Textron Jacobsen SLF530, Repair Manual

Page: 65 / 352

ELECTRICAL
673831-Rev A 4-21
4
Run Circuit—Theory of Operation
Unswitched Power Circuit
Unswitched power is available from the battery positive
terminal to the 3-way distribution block.
Unswitched power is available from the 3-way distribution
block to the following:
• 30-amp fuse (F3)
• 15-amp fuse (F4)
• 20-amp (F6)
• 20-amp fuse (F7)
Unswitched power is available from 30-amp fuse (F3)
output terminal to the ignition relay (K1) terminal 30.
Unswitched power is available from 15-amp fuse (F4)
output terminal to the following components:
• Ignition switch terminal 6
• LDU Display terminal 1-01
Unswitched power is available from 20-amp fuse (F6)
output terminal to the MCU (U1) terminals 6-06 and 6-07.
Unswitched power is available from 20-amp fuse (F7)
output terminal to the MCU (U1) terminals 1-01 and 1-01.
Switched Power Circuit (Green)
When the key switch (SW1) is turned to the run position,
voltage is provided from key switch terminal 4 to ignition
relay (K1) terminal
8 6, energizing the relay and to MCU
(U1) terminal 1-02.
With the ignition relay (K1) energized, switched power is
provided from ignition relay terminal
8 7 to the following
components:
• Fuel pump (M2)
• Mow Switch (SW2) terminal 2
• Seat switch (SW4) terminal 1
• Air ride seat switch (SW4A) terminal 3
• Parking brake (SW5) terminal 2
• Neutral Switch (SW7) terminal 1
• LDU display terminal 1-03
With switched power provided to the MCU, the MCU will
energize.
With switched power provided to the fuel pump, the fuel
pump starts to operate.
With switched power provided to the LDU, the LDU
display will energize and will display vehicle status.
Run Circuit—On Seat
The seat switch allows the engine to continue to operate
when the parking brake switch is in the off position,
traction pedal is not in neutral position or when the mow
switch is in the on position.
When the operator is on the seat, the seat switch
contacts close. With the seat switch contacts closed,
voltage is provided to MCU (U1) terminal 4-01.
With voltage provided to MCU terminal 4-01. The MCU
continues to provide voltage to the fuel shutoff hold-in
coil, keeping the fuel shutoff solenoid plunger retracted.
With the solenoid plunger retracted, fuel continues to flow
to the engine.
If the operator leaves the seat with the parking brake
switch in the off position, traction pedal out of neutral
position or with the mow switch in the on position, the
MCU will stop supplying power to the fuel solenoid
hold-in coil.,The fuel shutoff solenoid hold-in coil will
de-energize, stopping the flow of fuel to the engine. The
engine will stop.
Run Circuit—Off Seat
Before leaving the seat, the mow switch must be in the off
position, the parking brake switch must be in the on
position and the traction pedal in the neutral position.
With the interlocks set, the MCU terminal 2-06 continues
to provide voltage to the fuel shutoff hold-in coil, keeping
the fuel shutoff solenoid plunger retracted. With the
solenoid plunger retracted, fuel continues to flow to the
engine.