Principals Of Operation - Simplicity 1691682 Service & Repair Manual

5 Electrical Troubleshooting
General Information - Theory
INTRODUCTION
Tools Needed
• VOM (Volt-Ohm meter, multi-meter, or equivalent)
• Test Light.
• Jumper wires with clips at both ends.
Electrical System Changes
Early and later model Landlords may have different elec-
trical components. However, the basic configurations
and troubleshooting procedures given in this section still
apply. For instance: If the troubleshooting procedure
instructs you to test the clutch / brake pedal switch, and
your tractor doesn't have a clutch / brake pedal switch,
simply skip that step.
System Description
The tractor has four basic electrical systems: ignition,
charging, cranking, and the safety interlock system.
• The ignition system, contained in the engine, is con-
nected through a harness from the magneto to the
ignition switch and interlock module.
• The charging system replenishes lost power to the
battery. The alternator supplies power through a
wiring harness that is connected to a circuit breaker,
and then to the battery.
• The cranking system provides the high energy need-
ed to start the engine. Current is drawn from the bat-
tery, through the solenoid, to the starter when the
ignition switch is activated.
• The safety interlock system incorporates safety cir-
cuits for safe starting, operation, and shutdown under
unsafe conditions. It consists of the neutral safety
switch, PTO switch, "Operator present" seat switch,
clutch/brake switch, and the interlock module.

PRINCIPALS OF OPERATION

Ignition System
When the ignition switch is turned to OFF, the ignition
circuit closes and grounds the ignition coil stopping the
engine by terminating spark
When the ignition switch is in the RUN position, the igni-
tion circuit is open, allowing the engine to run.
Charging System
While the engine is running, current flows from the alter-
nator through a rectifier to the positive battery post and
charges the battery. The circuit breaker, normally
closed, opens if the circuit is shorted.
Cranking System
Battery voltage is present at the "B" terminal of the igni-
tion switch at all times (see Figure 8). Turning the igni-
tion switch to START supplies 12 volts to one of the sole-
noid coil terminals. Current is then passed through the
other solenoid coil post to the safety ground circuit. If all
safety switches are closed, the solenoid coil is grounded
engaging the solenoid and sending power to the starter.
If the PTO, transmission, or clutch/brake pedal is
engaged, or if the operator present seat switch is open--
the solenoid will not be grounded and the starter will not
crank the engine.
Safety Interlock System
The safety system can be divided into two sub-systems.
The first grounds the engine ignition module if the opera-
tor leaves the seat with the transmission engaged or the
PTO engaged.
If the operator leaves the seat, the engine will run only if:
-the PTO is disengaged, AND
-the the parking brake is ON, AND
-the ground speed control lever is in the neutral
gate.
The second sub-system prevents the engine from crank-
ing if the operator is not in the seat with the transmission
disengaged and the PTO disengaged.
The engine will crank only if::
-the operator is in the seat, AND
-the PTO is disengaged, AND
-the clutch / brake pedal is depressed, AND
-the groundspeed control lever is in the neutral
gate.
Operation
If the seat switch system is functioning properly, the fol-
lowing statements are true:
1. The engine will not start unless an operator is in the
seat.
2. The engine will stop running if the operator leaves his
seat while:
a.) the parking brake off, or
b.) the PTO is engaged, or
c.) the ground speed control lever is outside the neu-
tral gate.
3. If the operator is in the seat, the operator can engage
and disengage the transmission and PTO while
engine continues to run.
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