Service manual
Table Of Contents
(3) Inspection
of
brushes and
commutator
(a) Check the brushes for wear. A brush
worn
down
excessively should be replaced
by
a new one.
When the brush
is
replaced, grind the brush against
the
commutator
surface
by
using
#250
sandpaper
so
that
it makes a full-face
contact
with
the com-
mutator.
(b) Check the mica insulation for condition,
It
should
be
"undercut,"
that
is, the segment between two
adjacent mica should be slightly
proud
of
the mica
surface,
as
viewed in the cross section. Since the
commutator
surface
is
subject
to
gradual wear, a
point
will be reached in the course
of
service,
where the segments become flush
with
the mica.
If
the
commutator
in such a condition is
kept
in
service, the mica will
tend
to interfere
with
the
satisfactory commutation. Before this
point
is
reached, it
is
necessary to recondition the com-
mutator
surface
by
regrinding or sanding
with
#400
sandpaper and
to
undercut
the mica pro-
perly,
as
shown below:
Mica
Wrong
Right
Checking mica insulation
7-2 Alternator
(1) Alternator and regulator inspection before
disassembly
(a)
If
charging system
is
found defective, check
for items below before making adjustment or
repair:
•
Fan
belt
tension
• Loose connections, open short circuit in
charging system wiring
• Trouble
of
charging system due
to
defective
battery
(b)
Output
test
on
a test
bench
Remove the alternator from the engine.
Connect it in a test circuit
as
shown at
upper
right,
and operate it
by
a
motor
for testing.
Close the switches
Kl
and K2under the state
where very little load current flows in the test
circuit
by
varying load resistance
to
the max-
imum. Gradually increase alternator speed
-
85-
while keeping the terminal voltage
at
constant
13.5 volts, and read the ammeter at
2500
rpm.
The alternator
is
satisfactory
if
the ammeter
registers at least
30
amperes.
:
Amm,,,,
K1
~
..,.
Battery:
_v
Volt
met"
1
""
-
(c)
Output
test
on
a machine
Place a switch in the circuit between the
battery
and alternator. With the switch
kept
open, connect
an ammeter (60-ampere class) and a voltmeter
to the circuit.
Make sure
that
the voltmeter registers the
battery
voltage when the switch
is
closed.
Start
the engine, and
turn
on
the lamp switch.
Increase the engine (alternator) speed, and read
the ammeter when the alternator speed
is
5000
rpm. The alternator
is
satisfactory
if
the ammeter
registers at least
70%
of
the nominal
output.
[NOTE]
This test
is
a first-aid test.
It
is
recommended
that
the alternator be tested
on
a test bench for
close inspection.
+
Battery T
Volt
meter
,
,
~
I