Yamaha EF4500iSE Theory & Diagnostics Manual page 49

Check for resistance in the main coil, this model is
0.33 ohms, +10%, between the red and white wires
and the same between the brown and blue wires.
Then check the resistance in the sub-coil for 0.97
ohms, +10%, between the light green/red and the
green wires in the 4 pin connector.
There is also a battery charge coil inside the stator
assembly. If the complaint is everything works good,
except the battery keeps going dead. Check the
resistance between the two blue/white wires that are
in the 2 pin connector for 0.1 ohms, +10%.
If everything checks out OK there, test all three of
those coils for a short to ground. And if it still checks
out, test for them being shorted together. Be sure to
check between the main coil and the sub coil, the
main coil and the battery charge coil and the sub coil
and the battery charge coil.
If the problem was not found in the stator assembly,
then we'll move on to the rotor.
Remove the brush assembly and inspect them for
wear. The standard length is 12.5mm and the wear
limit is 9mm. Replace them and retest the generator
if they're below the wear limit. If they check OK, then
we'll test the rotor windings resistance while the
brushes are off.
Place the meter leads on the two slip rings that the
brushes ride on. The reading should be 55.1 ohms,
+10%.
If that is OK, test it for being shorted to ground by
placing one meter lead on one of the slip rings and
the other meter lead on the core of the rotor.
You should have an open circuit. Any resistance
reading would mean the windings are contacting the
core and the rotor must be replaced.
The last test will be the AVR circuit board. First rein-
stall the brush assembly, but do not connect the wire
leads. Disconnect the emergency relay unit and
start the engine.
Apply 12 volts DC to the brush terminals with the "+"
to "+" terminal and the "-" to "-" terminal.
Check the sub coil voltage between the light green/
red and the green wires for 53 volts AC. If the voltage
is correct, then the AVR board is bad and should be
replaced.
As with the AVR and Non-AVR models, one of these
tests should reveal the problem.
TESTING PROCEDURES FOR MODELS
EqUIPPED WITH DC CIRCUITRY
As mentioned with the EDL6500S, some other
Yamaha models also have DC 12 volt capabilities.
Models such as the early model non-inverter EF1000,
produce this voltage by tapping off of the main coil
and using a full wave rectifier to convert the AC volt-
age to DC.
On models like this, if the problem is only with the
DC portion of generator, it probably has a bad recti-
fier.
Test the rectifier according to the specific model's
Service Manual.
Because the DC circuit uses the main coil to provide
it's voltage, a problem with the AC side will more
than likely result in a problem with the DC side as
well.
As with the other coils, test for normal resistance,
short to ground and shorted to the sub-coil. If it is
part of the main coil it cannot be shorted to the main
coil, but be sure to check the Service Manual for the
model you are working on.
2-15
Generator Diagnostics