Service Manual
Alternator
Part Number
NN10734
Purpose
To produce current for battery charging, electric clutch and any other
electrical accessories on the tractor. Capacity: 20 Amps.
Alternator
How
It
Works
The alternator (or stator) is simply a coil of fine wire wrapped on an iron
core. As the magnet in the flywheel passes by
it,
current is produced.
Because a magnet has a north and south pole, half of the current
produced is in one direction and half is in the other. This type current is
AC or alternating current. There are no electronic components inside,
so
this alternator relies on an external regulator/rectifier to change the
output to DC (direct current.)
Testing
1. Disconnect the two wires coming from the alternator.
2. Start the engine, making sure that the alternator wires do not touch.
3.
Measure the voltage across the two alternator leads.
If
it is within 10%
of the voltage called out below, it is
OK.
Otherwise, go to step
4.
4.
With the engine off, measure the resistance across the two alternator
leads. It should fall in the range specified below. If not replace the
alternator.
5. With the engine off, measure the resistance between one alternator
lead and the iron core. It should show infinite resistance (no
continuity). Repeat this test for the other alternator lead. If either test
shows continuity replace the alternator.
Test
Reading
Voltage
@
1800 rpm
29 Volts
Voltage
@
3600 rpm 57 Volts
Alternator Resistance 0.10 to 0.19 Ohms
Clutch,
Part Number
Electric
78-6990
Purpose
Engages blade.
How
It
Works
A coil inside the clutch becomes an electro-magnet when energized.
Electric Clutch This draws the clutch plate to the clutch disk to set the blade turning.
Testing
1. Insure that the gap between clutch plate and clutch disk
is
.015”.
2. Apply twelve volts to clutch wires. Clutch plate should be drawn to
3. Connect volt/ohmmeter to clutch wires. Set scale to
R
X
1. Resistance
disc.
If
not, check resistance of coil.
should be 2.6 3.2 ohms. If not, replace clutch coil.
4