5 Amp AC - 3 Amp DC - Rectifier Plug Type
The dual circuit alternator is designed to operate as an
integral part of the engine and is separate from the
engine starting system. Recommended battery sizes
range from 20 ampere hour for warm temperature
service to 40 ampere hour in coldest service.
Fig. 166 - Dual Circuit Alternator
The dual circuit alternator is actually two separate
alternator systems. A single ring of magnets inside the
flywheel supplies the magnetic field for both of them.
One alternator system uses a solid state rectifier and
provides battery charging current. The other alternator
system feeds alternating current directly to the lights.
Since the two are electrically independent, use of the
lights does not reduce the charge going into the battery.
Fig. 167 - Typical Wiring Diagram
The battery is not used for the lights, so lights are
available even if the battery is disconnected or removed.
The alternator uses less than 0.2 horsepower.
Current for the lights is available as long as the engine is
running. The output depends upon engine speed.
Twelve-volt lights with a total rating of 60 to 100 watts
may be used. With lights rated at 70 watts, the voltage
rises from 8 volts at 2400 RPM to 12 volts at 3600 RPM,
so the brightness of the light changes with the engine
The current from the battery charging alternator is
unregulated and is rated at 3 amperes. The output rises
from 2 amperes at 2400 RPM to 3 amperes at 3600
There is one external connection. The battery charging
current connection is made through one terminal of a two
connector plug. Current for lights is available at the
second terminal of this plug. The plug is polarized to
prevent improper connections. The return circuit for both
alternators is through ground to the engine block.
CHECKING BATTERY INSTALLATION
Check if battery polarity is correct. Negative (-) side of
battery should be grounded to engine or frame; positive
(+) side of battery to alternator output lead. Figure 167.
WHEN CHECKING ALTERNATOR COMPONENTS,
MAKE THE TESTS IN THE FOLLOWING SEQUENCE:
TESTING ALTERNATOR CHARGING (DC) OUTPUT
Set #19236 VOA meter to measure amperes. Attach
leads in series with positive battery terminal and wire as
shown in Fig. 168. Meter should indicate output. The
charge range is dependent on the condition of the battery
and engine speed. If meter shows no charge or shows a
discharge, test diode and stator.
Fig. 168 - Testing Alternator DC Output