This will have more info than you need, but it is a cut and paste I have used for others..
GENERAL
Magneto
The purpose of the charging system is to keep the
battery at a full state of charge.
The magneto is the primary source of electrical
energy. It transforms magnetic field into electric
current (AC).
717 Engine
The magneto has a three-pole coil. Capacity is 160
watts.
947 Engine
The magneto has a 3 phase, “Y” wound stator on
18 poles. Capacity is 180 watts.
787 RFI and 947 DI Engines
The magneto has a 3 phase, delta wound stator
on 18 poles. Capacity is 270 watts.
Rectifier/Regulator
All Models
The rectifier receives AC current from the magneto
and transforms it into direct current (DC).
The regulator, included in the same unit, limits
voltage at a maximum level (14.5 to 14.8 volts) to
prevent any damage to components.
717 Engine
A half-wave rectifier receives magneto AC current
and transforms it into direct current (DC) to allow
battery charging.
947 Engine
A dual 1/2 wave series rectifier receives the magneto
AC current and transforms it into direct current
(DC) to allow battery charging.
787 RFI and 947 DI Engines
The unit is using a 3 phase in series rectifier/regulator
which transforms (AC) from the magneto into (DC) to
allow battery charging.
TESTING PROCEDURE
NOTE: First, ensure that battery is in good condition
prior to performing the following tests.
Rectifier/Regulator
NOTE: All models with a 947 engine, the rectifier/
regulator is integrated in the MPEM.
STATIC TEST: CONTINUITY
Due to internal circuitry, there is no static test available.
DYNAMIC TEST
Current Test
Carburetor-Equipped Engines and 947 DI
Engines
Proceed as follows:
– Start engine.
– Lay an inductive ammeter on positive cable of
battery.
– Bring engine to approximately 6000 RPM.
Current reading should be approximately 4 amperes
for the 717 engine and 5 amperes for the 947
carburetor-equipped and 947 DI engines. If not,
check magneto output prior to concluding that rectifier
is faulty.
