Yamaha YFZ450S 2003 Service Manual page 355

2. The tail/brake light fails to come on.
1. Tail/brake light bulb and socket
• Check the tail/brake light bulb and socket
for continuity.
Refer to "CHECKING THE BULBS AND
BULB SOCKETS".
• Are the tail/brake light bulb and socket
OK?
YES
2. Voltage
• Connect the pocket tester (AC 20 V) to the
tail/brake light coupler as shown.
Tail/brake light coupler (wire harness side)
Tail/brake light
Positive tester probe → blue 1
Negative tester probe → black 2
L
B
• Set the main switch to "ON".
• Start the engine.
• Measure the voltage (AC 12 V) of blue 1
on the tail/brake light coupler (wire har-
ness side).
• Is the voltage within specification?
YES
This circuit is OK.
NO
Replace the
brake light bulb,
socket or both.
1
Y Y L
B
2
NO
Replace the rectifier/
regulator.
LIGHTING SYSTEM
tail/
8 - 32
– +
ELEC