Service manual
ALTERNATOR
TESTING
DESCRIPTION
The charging system consists
of
an alternator with a voltage
regulator, an engine
DC
wiring harness, a mounted
DC
cir-
cuit breaker and a battery with connecting cables. Because
of
the use
of
integrated circuits (IC's), the electronic voltage
regulator is very compact and is mounted internally
or
on
the
back
of
the alternator.
#14
BROWN
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#14
GREY==~~-+
__
1.
Start
the
Engine.
2. After a few minutes
of
running measure the starting bat-
tery voltage at the battery terminals using a multi-meter
set
on
DC
volts.
The voltage should be increasing toward
14 volts.
If
it is,
the
alternator is working.
Tum
to Step 4 .
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o
MULTIMETER
COM
#14
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to
Fuel
Solenoid
&
Fuel
Lin
Pump
#14
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~~;=#14
BROWN
#14
PINK
to
Tachomel8r
,
51
AMP
ALTERNATOR
x
(GENERATOR)
'\'\'---;,"
i~~~~=
1#10'RED
GROUND
TROUBLESHOOTING
A
WARNING:
A failed
alternator
can
become
very
hot.
Do
not
touch
until
the
altemator
has
cooled
down.
This troubleshooting section is to determine
if
a problem
exists with the charging circuit
or
with the alternator.
If
it
is
determined that the alternator
or
voltage regulator is bad, it is
best to have a qualified technician check
it
out.
The alternator charging circuit charges the starting battery and
the service battery.
An isolator with a diode, a solenoid, or a
battery selector switch is usually mounted in the circuit to iso-
late the batteries so the service battery is not discharged along
with the service battery.
If
the alternator is charging the start-
ing battery but not the service battery, the problem is in the
service battery charging circuit and not with the alternator.
Testing
the
Alternator
A
WARNING:
Before
starting
the
engine
make
certain
that
everyone
is
clear
of
moving
parts!
Keep
away
from
sheaves
and
belts
during
test
procedures.
A
WARNING:
MULTIMETERS
AND
DC
CIRCUnS:
DC
and
AC
circuits
are
often
mixed
together
in
marine
applications.
Always
disconnect
shore
power
cords,
isolate
DC
and
AC
converters
and
shut
down
generators
before
performing
DC
testing.
No
AC
tests
should
be
made
without
proper
knowledge
of
AC
circuits.
B+OUTPUT
to
Starter
Motor
TESTING
THE
STARTING
BATTERY
-
ALTERNATOR
(ENGINE
RUNNING)
_
GROUND
3.
If
the starting battery voltage remains around
12
volts
after the engine is started and run for a few minutes, a
problem exists with the alternator
or
the charging circuit.
a. Turn off the engine. Inspect all wiring and connections.
Ensure that the battery terminals and the engine ground
connections are tight and clean.
A
CAUTION:
To
avoid
damage
to
the
battery
charging
circuit,
never
shut
off
the
engine
battery
switch
when
the
engine
is
running!
h.
If
a battery selector switch is in the charging circuit,
ensure that
it
is on the correct setting.
c. Tum on the ignition switch, but do not start the engine.
d.
Check the battery voltage.
If
your battery is in good
condition the reading should be
12
to
13
volts.
Engines & Generators
50