John Deere stx38 User Manual
Page 132
4 - 48
3/21/97
CIRCUIT OPERATION AND DIAGNOSIS
ELECTRICAL
CHARGING CIRCUIT OPERATION
STX38 (SN 210001— ) & STX46
Function:
To maintain battery voltage between 11.8 and 13.2.
Operating Conditions:
The engine must be running for the charging system to
operate.
Theory of Operation:
The charging system is of the permanent magnet and
stator design. Charging output is controlled by
regulator-rectifier (N1).
The key switch (S1) must be in the RUN position and
the engine running for the charging circuit to be fully
operational.
As the flywheel turns, several permanent magnets
(located on the inside lip of the flywheel) induce AC
current in the stator (G2) windings. The AC current
flows through two white wires to the regulator-rectifier
(N1). The regulator-rectifier (N1) converts AC current to
DC current needed to charge the battery (G1).
The battery (G1) voltage is sensed by the regulator-
rectifier (N1) through the short, black wire of the
regulator-rectifier, the positive battery cable (red), and
the red wire (220) between the starter solenoid (K1)
and engine connector. This allows the regulator-
rectifier to monitor battery voltage; if battery voltage is
low, rectified DC current is released to charge the
battery. When the battery is fully charged, the regulator
stops the flow of the rectified DC current to the battery.