Service manual
ALTERNATOR
TESTING
e. Now check the voltage between the alternator output
tenninal (B+) and ground.
If
the circuit is good, the
voltage at the alternator should be the same as the
bat-
tery, or
if
an isolator is in the circuit the alternator volt-
age will be zero.
If
not, a problem exists in the circuit
between the alternator and the battery. Check all the
connections
-look
for
an
opening in the charging cir-
cuit.
TESTING
THE
STARTING
BATTERY-ALTERNATOR
(ENGINE
RUNNING)
.
ENGINE
~::::.--'
GROUND
f.
Start the engine again. Check the voltage between the
alternator output and ground.
The voltage reading for a properly operating alternator
should
be
between13.5 and 14.5 volts.
If
your alterna-
tor is over- or under-charging, have it repaired at a reli-
able service shop.
NOTE:
Before removing,the alternator for
repair;
use
a
volt-
•
meter
to
ensure
that
12
volts DC excitation
is
present at
the
EXC terminal if
the
previous
test
showed only battery voltage
at
the
B output
terminal.
If
12
volts
are
not present at
the
EXC terminal, trace
the
wiring looking for
breaks
and poor connections.
Alternator
is
Working
5. Check the voltage
of
the service battery. This battery
should have a voltage between
13
and
14
volts when
the
engine is running.
If
not, there is a problem in the service
battery charging circuit. Troubleshoot the service battery
charging circuit by checking the wiring and connections,
the solenoid, isolator, battery switch and the battery itself.
(KID
MULTI
METER
0
COM
SERVICE
BATIERY
TESTING
THE
SERVICE
BATTERY
(ENGINE
RUNNING)
A
CAUTION:
When
perfonning
tests
on
the
altemator
charging
circuit
do
not
use
a
high
voltage
tester
(i.e.
Megger).
You
can
damage
the
altemator
diodes.
ALTERNATOR
INSPECTION
When rebuilding the engine. The alternator
~hould
be cleaned
and inspected. The housing can be wiped off with a solvent
and the alternator tenninal studs should
be
cleaned with a
wire brush. Make certain those studs are tight. Also clean the
wiring connections that connect to the wiring harness.
Turn the rotor pulley by hand. It should turn smoothly.
Depending on when the alternator was last serviced, the
brushes may need replacing.
If
the alternator is at all suspect,
send it to a service shop for testing and overhaul.
Engines & Generators