Westerbeke 12C-TWO Operator's Manual page 43

ALTERNATOR TESTING
e. Now check the voltage between the alternator output
terminal (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
STARTING BAmRY
ALTERNATOR
TESTING 11IE STARTING
BATTERY • ALTERNATOR
(ENGINE RUNNING}
MULTIMETER
..c::~--1
ENGINE
GROUND
£
Start the engine again. Check the voltage between the
alternator output and ground.
The voltage reading for a properly operating alternator
should be between 13.5 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 voltmeter 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
4. 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
ba~ery
chargina circuit by checking the wiring and connections,
the
sole~oid,
isolator, battery switch and the battery itself.
MULTIMETER CKQ)
0
COM
SERVICE
BAmRY
TESnNG 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 alternator diodes.
ALTERNATOR INSPECTION
When rebuilding the engine. The alternator should be cleaned
and inspected. The housing can be wiped off with a solvent
and the alternator terminal 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.
Tum the rotor pulley by hand. It should tum 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.
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