John Deere stx38 - Manual (Page 150)

4 - 66
3/21/97
TESTS AND ADJUSTMENTS ELECTRICAL
STARTER SOLENOID TEST
Reason:
To determine if starter solenoid or starter is defective.
IMPORTANT: STX38 Serial Numbers
(STXH270001—277450)
(STXJ270001—275010)
(STXH270001— )—If the starter pinion fails
to disengage from flywheel the steel and nylon
washers in the bendix of the starter are
reversed. Correct order is spring, steel washer,
nylon washer, spring retainer, retainer ring, and
dust cap.
Equipment:
• Jumper wire
Connections:
1. Put transaxle in neutral. Move key switch to off
position.
2. Engage park brake.
3. Disconnect and ground spark plug lead.
4. Disconnect purple wire from small starter solenoid
engagement terminals (A).
Procedure:
1. Connect jumper wire to positive battery terminal
and briefly jump to bare small starter solenoid
engagement terminal (A). All solenoid terminals
should be clean and free of corrosion.
Results:
• Starter runs: solenoid is good, check circuit wiring.
• Starter does not run: go to step 2.
2. Connect jumper wire between starter solenoid large
terminals (B and C).
Results:
• Starter runs: Replace solenoid.
• Starter does not run: Check battery cables then
replace starter.
STARTER AMP DRAW TEST
Reason:
To determine the amperage required to crank the
engine and check starter motor operation under load.
Equipment:
• JTO5685 Battery Tester
• Photo Tachometer
Connections:
1. Put transaxle in neutral. Engage park brake.
2. Test system ground connections and battery.
3. Turn knob (A) of tester counter-clockwise to off.
4. Connect red clamp of battery tester to positive
terminal of battery and black clamp of tester to
negative terminal of battery.
5. Install tachometer reflective tape on flywheel
screen.
6. Remove spark plug high tension lead and ground to
engine.
Procedure:
1. Crank engine and read voltage on DC voltage scale
of battery tester and check engine rpm.
2. Turn key switch to off position.
IMPORTANT: Perform the following procedure
within 15 seconds to prevent electrical damage
to components.
3. Turn knob of battery tester clockwise until the DC
voltage is the same as when cranking.
4. Read DC amperage on battery tester.
5. Turn load knob fully counterclockwise.
Specifications:
Maximum starter amp draw
. . . . . . . . . . . . . . . . . . . . . . . . 180 amps at 225 rpm
Results:
• If amperage is above specification, or rpm is low,
check starter for binding or damaged.
• If starter is good, check internal engine, traction or
PTO drive for binding or damage.
M55914
A
C
B
A
M55943