John Deere 318 - Manual (Page 310)

CHARGING CIRUIT OPERATION
The function of the charging circuit is to keep the
battery properly charged by supplying approximately
13.6—14.7 VDC to the battery while the engine is
operating.
The charging system is a permanent magnet and
stator type. The magnets are located in the flywheel,
which rotates around the stationary stator (G2)
windings. Current output is controlled by voltage
regulator/rectifier (N1), mounted separately from the
stator. Battery discharge lamp (P4) warns the
operator when battery discharge lamp control (A)
senses low battery voltage. The battery discharge
lamp and lamp control DO NOT monitor current
output from the stator.
As the flywheel turns, the permanent magnets induce
alternating current (AC) in the stator windings. The
alternating current flows to the voltage
regulator/rectifier. The rectifier portion of the voltage
regulator/rectifier converts the alternating current to
direct current (DC). The regulator portion stabilizes
the direct current and increases or decreases current
flow as required by the battery.
Battery discharge lamp control (A) senses battery
voltage present at fuse (F2). If the lamp control
senses low voltage (less than 12.3 volts), it will
provide a path to ground for battery discharge lamp
(P4). Since battery voltage is always available at the
discharge lamp when the key switch is in the RUN or
START position, the ground path provided by the
lamp control will allow battery current from fuse (F1)
to flow through the battery discharge lamp to ground,
lighting the discharge lamp. The lamp will stay on
until battery voltage increases to 12.7 volts. At this
point, the battery discharge lamp control will break
the path to ground, turning the battery discharge lamp
off.
Fuses (F1 and F2) protect the battery discharge lamp
and lamp control circuit from excessive current.
NOTE: (*) For machines (S.N. —475000), a light
green wire is used instead of the 210 red wire
used on later machines. The green wire
connects to terminal “B” of key switch (S1),
instead of connecting to circuit breaker (F3).
NOTE: 1. The illustration shows ground circuit for
machines (S.N. 475001— ).
For machines (S.N. —475000), the blk wire
from the TDC module 2-pin connector
terminates (grounds) at the right side of the
pedestal panel.
MX,159024020,7 -19-16MAY95
Component Location and Operation/Theory of Operation
TM1590 (17MAY95)
240-15-8
316, 318 & 420 Lawn and Garden Tractors
020895
240
15
8