Alternator Testing - Westerbeke BTG 8.5 Operator's 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.
TROUBLESHOOnNG
A
WARNING:
A failed altemator can bectJIIIe very
hot.
Do
not touch until the alternator has csoled dswn.
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 n:gulator 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 ffDIII
sheaves and belts during
test
pmcedures.
A
WARNING:
MOLT/METERS AND DC CIRCUITS:
DC and AC circuits are often mixed together in marine
applfcatiiJIIS. 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 pmper knowledge of AC circuits.
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 .
MULTIMETER
TESTING THE STARTING
BATIERY • ALTERNATOR
(ENGINE RUNNING)
rnm
0
COM
'
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. Thm 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!
b. 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.
TESTING THE
BATTERY VOLTAGE
EN_GINE NOT RUNNING
~--tMULTIMETER
I...,.,.IWESTERBEICE
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Engines & Generators
-::- GROUND
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