Westerbeke 12C- TWO Operator's Manual page 33

ALTERNATORS TESTING/TROUBLESHOOTING
TESTING THE ALTERNATOR
A
CAUTION:
Before starting the engine make
certain that everyone Is clear of moving parts! Keep
away from sheaves and belts during test procedures.
1. Start the engine.
2. After the engine has run for a few minutes, measure the
starting battery voltage at the battery tenninals using a
multimeter set on DC volts.
a. If the voltage is increasing toward 14 volts, the
altemator is working; omit Steps 3 through 8 and go
directly to "Checking the Service Battery."
b. If the voltage remains around 12 volts, a problem
exists with either the altemator or the charging circuit;
continue with Steps 3 through 8.
3. Thrn 00' the ·engine. Inspect all wiring and connections.
Ensure that the battery terminals and the. engine ground
connections
are
tight and clean.
4. If a battery selector switch is in the charging circuit,
ensure that it is on the correct setting.
S. Thrn on the ignition switch, but do not start the
engine. .
6. Check the battery voltage. If the battery is in good
condition, the reading should be 12 to 13 volts.
. MEASURING
;--:-,-/~q •
BAITelIY VOLTAGE
ENGINE RUNNING
'li~~~~
,MEASURiNG 6
.",...~
. .
BATIERY VOLTAGE
'(lGN.ITION ON
TESTING THE OUTPUT CIRCUIT
1. Connect the positive probe to the output terminal Band
connect the negative probe to ground ..
2. Wiggle the engine wiring harness while observing the
vol!I)leter. The meter should indicate the appro~imate
. battery voltage, and should not vary. If
no
reading is
obtained, or if the reading varies, check the alternator
output circuit for loose or
dirty
connections or
damaged wiring.
3. Start the engine.
4. Repeat the same measurelhent, the negative probe to
ground, the positive probe to B with the engine running:
The voltage reading shouidbe between 13.5 and 14.5
volts. If your altemator is over or under-charging, have
it repaired at a reliable service shop.
S. If the previous test reads
ani)'
battery voltage at
terminal B, use the meter to measure the DC excitation
terminal. If 12 volts is not present at exciter terminal R,
inspect the wiriIlg for breaks and poor connections.
Jump 12 volts from a 12 volt source (such
is:
the ..
battery) and operate the alternator. If the voltage' output
is 13-14 volts, . then the alternator is OK .
TESTING THE OUTPUT
CIRCUIT
ENGINE RUNNING
EXCITER
'TERMINAL
"R
(+)
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.
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.WESTERBEKE
Engi,;e~
&
Generators
26