Westerbeke W-27 Service Manual

DC ELECTRICAL SYSTEM
DESCRIPTION
The DC Circuit functions to start, operate and stop the gener~
ator's engine. The circuit is best understood by reviewing the
DC ELECTRICAL SYSTEM WIRING DIAGRAMS.
The engine's DC wiring is designed with three simple basic
circuits:
preheat, slart, and run or stop.
Engine 12-Volt Control Circuit
The engine has a ] 2 volt DC electrical control circuit that is
shown in the wiring diagrams. Refer to these diagrams when
troubleshooting or when servicing the DC electrical system
on the engine.
A CAUTION: To avoid damage to the battery charg-
ing circuit, never shut 0" the engine battery switch
while the engine is running. Shut off the engine battery
switch, however, to avoid electrical shorts when
working on the engine's electrical circuit.
CHARGING SYSTEM
The charging system consists of an alternator, a voltage
regulator, an engine DC wiring harness,
an engjne~mounted
DC circuit breaker, a battery and connecting wires. 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.
ALTERNATOR TROUBLESHOOnNG
If you suspect that the alternator is not producing enough
voltage
to charge the engine's battery, check the following:
A WARNING: A failed aftemator can become very
hot. Do not touch until the alternator has cooled down.
o Make certain your alternator is securely mounted.
o Check the drive belts for proper tension.,
o Inspect for loose or disconnected wires at the alternator.
MANDO
51 AMP AlTERNATOR
NOTE: An isolator with a diode, a solenoid, or a ballery
selector switch
is usually mounted in the circuit to isolate the
balleries
so the starling battery is not discharged along with
the house batteries.
If the isolator is charging the starting
battery
but not the house battery, the alternator is OK and
the problem
is in lhe battery charging circuit.
A WARNING: Shut off the engine battery switch or dis-
connect from the battery when working on the engine
electrical system.
Checking for Proper Voltage
If you suspect the alternator has failed, perform the folJowing
tests with the engine off:
1. Using a voltmeter, connect the
voltmeter red wire clip to
the
output terminal B.
2. Connect
the voltmeter negative wire to any ground on the
engine.
3. Check the battery voltage. If the battery is
in good condi~
tion it should read ]2 to 12.5 volts.
4. Check the voltage between the alternator (+) positive
terminal B and any engine ground. If the circuit
is good,
the voltage at the alternator should be the same as the
battery (unless there's an isolator
in the circuit, then the
reading
would be zero).
A CAUTION: To avoid damage to the battery chalg ..
ing citeuit, never shut off the engine battery switch
when the engine is running!
A WARNING: Before stalfing the engine make cel-
fain that everyone is clealof moving parts! Keep away
from sheaves and belts during test procedures.
5. Start the engine.
6. The voltage reading for a properly operating alternator
should indicate between
13.5 and 14.5 volts. If your
alternator is over-
or uncercharging, have it repaired at a
reliable service shop.
NOTE: Before removing the alternator for repair, use your
voltmeter to ensure that] 2 volts DC excitation is present
at the
EXC lerminal if the previous test showed only bat-
tery vollage at the B oUlput terminal.
Engines & Generators
58

Westerbeke W-27 Specifications

General

Brand	Westerbeke
Model	W-27
Category	Engine
Language	English