Output Test; Disassembly - Westerbeke 38B FOUR Service Manual

ALTERNATOR/REGULATOR SERVICE
The voltage reading for a properly operating alternator
should be between 13.5 and 14.5 volts. If your alternator is
over- or undercharging, have
it
repaired at a reliable service
shop, or continue with the following tests.
NOTE:
Before removing the alternator for repair, use your
voltmeter to ensure that I2 volts DC excitation is preselll at
the R (£XC) terminal if the previous tesi showed only battery
voltage at the B output terminal.
+
Output Test
1.
Disconnect the battery ground cable.
2. Disconnect the wire from terminal B on the alternator
and connect an ammeter between B and this wire.
3. Connect a voltmeter between terminal B (+) and ground (-).
4. Connect to the P terminal.
5. Reconnect the battery ground cable to the (-) tenninal.
The voltmeter should indicate the battery voltage.
6. Connect B+ to the R terminal (regulator).
7. Start the engine.
S. Tum on 12 volt accessories equaling the amperage output
of the alternator, accelerate the engine to the specified
speed (2000 to 3000 rpm) and measure the output cur-
rent. The output current should be close to the alterna-
tor's maximum ouput.
Output Current 1300 rpm 2500
rpm
5000
rpm
Hot 16 amp
41 amp
48 amp
Cold 24 amp 50
amp
NOTE:
rpm is thaI of the alternator. The pulley ratio
(alternator vs crank pulley) is 1.78
to
1; all readings are
at
j
3.5 liolts.
OUTPUT TEST SETUP
DISASSEMBLY
1. After removing the three assembly through-bolts, insert a
screwdriver between the front bracket and stator. While
prying it, remove the front bracket and rotor.
NOTE:
If the screwariver is inserted too deep, the slOtor
coil might be damaged.
2. Hold the rotor in a vise and remove the pulley nut. Then
remove the pulley, fan, spacer and seal. Next, remove the
rotor from the front bracket and remove the seal.
3. Unsolder the rectifierfrom the stator coil lead wires and
remove the stator assembly.
NOTE:
Make sure that the solder is removed quickly (in
less than five seconds). If a diode is heated to more than
I50
a
C (310°F), it might be damaged.
4. Remove the condenser from terminal B.
5. Unsolder the plates Band L from the rectifier assembly.
6. Remove the mounting screw and B terminal bolt and
remove the electronic voltage regulator and brush holder.
The regulator and brush holder cannot be sepearated.
7. Remove the rectifier assembly.
S. Brush and brush spring replacement:
When only a brush or brush spring is to be replaced,
it
can
be
replaced without removing the stator, etc. With the brush
holder assembly removed, unsolder the pigtail of the brush.
NOTE:
If the terminals Land B of the rectifier assembly are
bent, damage might result
to
the rectifier. Therefore, the
plates Band L should be gently bent at the center.
RECTIFIER
ASSEMBLY
SPACER ROTOR
TERMINAL B BOLT
REGULATOR &
BRUSH HOLDER
STATOR
........ REAR
BRACKET
Engines & Generators
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