0003
TM 1-1740-221-13&P&P
THEORY OF OPERATION - (CONTINUED)
ELECTRICAL SYSTEM
General Information
The electrical system (FO-1) consists of two 12-volt maintenance free batteries connected in parallel to provide the
cranking amps necessary for starting. Electrical power to keep the batteries charged is supplied by a belt-driven 90
amp alternator mounted on the front of the engine. It produces three-phase alternating current and voltage, rectiied
to DC. The alternator does not require a cutout relay. A current regulator is an integral part of the alternator. This
current regulator determines output current depending on the load, such as headlights, rear lights, etc.
The starter motor is a gear reduction type and is used to turn the engine fast enough to start the engine. A starter
lockout switch prevents starter and ring gear damage when engine is running. The vehicle starts only in park and
the hand brake engaged. All circuits are protected with circuit breakers and/or fuses.
Two headlights are on the front of the vehicle. The stop/tail lights and rear backup lights are in the rear.
Turn signal lights are below the headlights on the front and combined with the taillights on the rear.
ELECTRICAL SYSTEM, FO-1
BATTERY CIRCUIT
Battery positive power is applied to the open contacts of the engine starter motor and the starter relay contacts
(SR) and also through the 80 amp Glow Plug thermal circuit breaker CB1 to the open contacts of glow plug relay
(GP), to the alternator battery output terminal and also through a 30 amp fuse 3FU to the battery contact terminal
on the ignition switch and also through a 20 amp fuse 9FU to the open contacts of transmission circuit relay (CRT).
Battery power is also applied through a 60 amp fuse 2FU to the open contacts of the accessory relay (CRA).
IGNITION SWITCH CIRCUITS
Ignition switch in the run position, battery power is applied through a 5 amp fuse 8FU to the hold position on the
fuel solenoid 50 also through a 10 amp fuse 5FU to the transmission ECU, through a 5 amp fuse 8FU which
energizes the transmission circuit relay (CRT) also through the hand brake limit switch (hand brake lever engaged)
energizing the starter interlock relay (CRSI), the hand brake relay (CRHB) and then power is also applied to the
hand brake on indicator light on the panel which now illuminates. Also, power is applied to the accessory relay
(CRA) from the ACC terminal on the ignition switch in the run position.
When the ignition switch is placed in the start position, battery power is applied to the starter relay (SR) (FO-1, line
9) as long as the starter interlock relay (CRSI) is energized (hand brake lever engaged) and the park relay (CRS) is
energized (transmission shifter in the park position).
With the start relay (SR) energized a set of contacts (FO-1, line 2) is closed which applies power to the pull side of
the fuel solenoid (max fuel position) and applies power to the starter solenoid which when energized closes the
starter motor contacts allowing the Kubota engine to be started.
Ignition switch in the run position, power is applied through a 5 amp fuse 7FU to the panel indicator lights and
gauges. With power applied to this circuit, the following occurs:
HOUR METER (G1) Records Engine Operating Hours
NOT OPERATIONAL until engine is started, engine oil pressure closes the normally open oil pressure switch,
therefore the hour meter only records actual engine operating hours.
00035
