4-22 4181383 First Edition
ELECTRICAL
4
Start and Glow Plug Circuit—Theory
of Operation
Power Circuit
Unswitched power is available from the battery positive
terminal to the starting motor battery terminal and then
from the starting motor battery terminal to 50 amp
thermal circuit breaker battery terminal. Unswitched
power is available through the 50 amp thermal circuit
breaker to start and glow plug relays terminal 30.
Unswitched power is available from 50 amp thermal
circuit breaker battery terminal to key switch terminal A
and control module terminal J3-6.
When the key switch is turned to the run position, voltage
is provided from key switch terminal B to control module
switch power input terminal J3-2, powering up the control
module and energizing the internal switched power relay.
Voltage is also provided from key switch terminal B to
control module select 2 input terminal J4-2, activating the
input. With the select 2 input activated, the control
module selects the software program for this machine.
This allows the control module to be used in more than
one machine.
With the internal switched power relay energized,
switched power is available from switched power relay
terminal 87 to control module terminal J3-3. Switched
power is available from control module terminal J3-3 to
splice 90. From splice 90, switched power is available to
the engine oil pressure light. Switched power is available
from the engine oil pressure light to the hydraulic filter
pressure light and then from the hydraulic filter pressure
light to the glow plug light.
With the internal switched power relay energized,
switched power is available from switched power relay
terminal 87 to control module terminal J3-5. Switched
power is available from control module terminal J3-5 to
splice 100.
From splice 100, switched power is available to the park
brake and neutral proximity switches.
With the key switch in the run position, the control module
performs a control panel lamp check for approximately 4
seconds. At the same time the control module performs a
horn test. During the test the horn will chirp six times.
Start and Glow Plug Circuits
To start and operate the engine with the operator off or
on the seat, the mow switch must be in the off position
and the following interlock switches must be activated:
• Park brake proximity switch
• Neutral proximity switch
With the brake pedal in the locked position, the brake
pedal linkage is brought near the magnetic target zone of
the park brake proximity switch, activating the switch.
With the switch activated, voltage is provided from the
proximity switch to control module park brake switch input
terminal J1-7, activating the input.
With the traction pedal in the neutral position, the traction
pedal linkage is brought near the magnetic target zone of
the neutral proximity switch, activating the switch. With
the switch activated, voltage is provided from the
proximity switch to control module neutral switch input
terminal J1-2 activating the input.
With the interlock switch inputs satisfied, control module
fuel hold output terminal J2-7 provides voltage to the fuel
shutoff solenoid hold-in coil, energizing the coil. Voltage
is also provided from fuel hold output terminal to the fuel
pump, turning on the pump.
When the key switch is momentarily turned to the start
position, the control module activates the glow plug
circuit. The control module activates the glow plug circuit
between 1-6 seconds depending on the coolant
temperature. The control module will not allow engine
cranking until the glow plug circuit has timed out.
The key switch can be held in the start position and the
control module will activate the start circuit after the glow
circuit times out.
With the key switch in the start position, voltage is
provided from key switch terminal C to control module
start input terminal J1-5, activating the input. With the
start input activated, the control module activates the
glow plug circuit.
To activate the glow plug circuit, control module glow plug
relay output terminal J2-6 provides voltage to glow plug
relay terminal 86, energizing the relay. With the relay
energized, voltage is provided from glow plug relay
terminal 87 to the glow plugs, heating the glow plugs.
Control module glow plug light output terminal J2-11
provides a ground to the glow plug light, turning on the
light.
To activate the start circuit, control module start relay
output terminal J2-5 provides voltage to start relay
terminal 86, energizing the relay. With the relay
energized, voltage is provided from start relay terminal 87
to the starter solenoid, energizing the solenoid. With the
starter solenoid energized, voltage is provided from the
starter solenoid contacts to the starter motor, engaging
the motor. The control module will only allow the start
circuit to operate for a maximum of 10 seconds.
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