Checking The Rectifier/Regulator; Checking The Radiator Fan Motor (For Jpn); Checking The Coolant Temperature Sensor - Yamaha YZ 2015 Series Owner's Service Manual

b. Measure the stator coil resistance.
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CHECKING THE RECTIFIER/REGULATOR

EASB291361
1. Check:
• Charging voltage
Out of specification  Replace the rectifier/
regulator.
Charging voltage
14 V at 5000 r/min
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a. Set the digital tachometer to the ignition coil.
b. Connect the pocket tester (DC 20 V) to the
rectifier/regulator coupler as shown.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Red "1"
• Negative tester probe 
Black "2"
c. Start the engine and let it run at approxi-
mately 5000 r/min.
d. Measure the charging voltage.
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EASB291362
1 2 3
1 2
8-65
ELECTRICAL COMPONENTS
CHECKING THE RADIATOR FAN MOTOR
(For JPN)
1. Check:
• Radiator fan motor
Faulty/rough movement  Replace.
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a. Disconnect the radiator fan motor coupler
from the wire harness.
b. Connect the battery (DC 12 V) as shown.
• Positive battery terminal 
Blue "1"
• Negative battery terminal 
Black "2"
1
L
c. Measure the radiator fan motor movement.
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CHECKING THE COOLANT TEMPERATURE EASB291363
SENSOR
1. Remove:
• Coolant temperature sensor
EWA
WARNING
• Handle the coolant temperature sensor
with special care.
• Never subject the coolant temperature
sensor to strong shocks. If the coolant
temperature sensor is dropped, replace it.
2. Check:
• Coolant temperature sensor resistance
Out of specification  Replace.
Coolant temperature sensor re-
sistance
2510–2780  at 20 °C (2510–
2780  at 68 °F)
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a. Connect the pocket tester (  1k/100) to
the coolant temperature sensor.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
2
B
12V