John Deere stx38 - Manual (Page 140)

4 - 56
3/21/97
CIRCUIT OPERATION AND DIAGNOSIS ELECTRICAL
PTO AND HEADLIGHTS CIRCUITS
OPERATION
STX38 (SN 210001— ) & STX46
Function:
To provide power to energize the PTO clutch and
headlights (optional).
Operating Conditions:
PTO—
The key switch (S1) must be in the RUN position, the
seat switch must be DEPRESSED (operator ON the
seat), the brake switch must be turned OFF (brake
pedal released), and the PTO switch (S2) must be
ENGAGED.
Headlights—
The key switch (S1) must be in RUN position and the
optional headlight switch (S5) must be pushed ON
(ENGAGED).
Theory of Operation:
PTO—
The PTO circuit uses the ignition circuit to stop the
engine if the operator gets off the seat with the PTO
engaged.
Current flows from the battery (G1) positive terminal to
the key switch (S1) via the starter solenoid (K1)
connection point, fusible link (F1) 201 light orange wire,
and 200 red wire. With the key switch (S1) in the RUN
position, current flows to the PTO switch (S2) via the
400 yellow wire.
The seat switch must be ENGAGED (operator ON the
seat) to prevent a path to ground for the ignition circuit
through the turned OFF (released) brake switch,
allowing the engine to RUN and power the PTO drive
sheave.
When the PTO switch (S2) is moved to the ON position
(ENGAGED), current flows through the PTO switch
(S2) and 750 blue wire to energize the PTO clutch (Y1)
windings. The energized PTO clutch magnet pulls the
PTO clutch brake away from the sheave plate, allowing
the sheave plate to turn with the engine crankshaft.
If the operator gets OFF the seat, the seat switch
creates a path to ground for the ignition circuit and the
engine kills. Once the engine has been killed, the PTO
switch (S2) must be pushed into the OFF position
before the cranking circuit can be engaged to restart
the engine.
Headlights—
Current flows from the battery (G1) positive terminal to
the key switch (S1) via the starter solenoid (K1)
connection point, fusible link (F1) 201 light orange wire,
and 200 red wire. With the key switch (S1) in the RUN
position, current flows to the PTO switch (S2) via the
400 yellow wire. At this tie point, current flows through
the 450 yellow/white to the headlights switch (S5).
When the headlights switch (S5) is pushed ON
(ENGAGED), current flows through the 451 yellow/
white wire through the headlights kit harness yellow
wire into the two red wire to the twin headlights, then to
engine ground (W2) via the black wires of the
headlights kit harness and the tractor harness 120
black wire.
The headlights are turned OFF by turning off the
headlights switch (S5) or the key switch (S1).