Yamaha YFM250RX 2008 Service Manual page 297

2. The tail/brake light fails to come on.
1. Tail/brake light bulb and bulb socket
(4D31)
• 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. Tail/brake light (4D35, 4D39)
• Disconnect the tail/brake light coupler.
• Connect the battery (12 V) to the tail/brake
light coupler terminals as shown.
• When the jumper leads are connected to
the terminals, the tail/brake light should illu-
minate.
Positive battery terminal → blue
Negative battery terminal → black
• Is the tail/brake light OK?
YES
NO
Replace the tail/brake
light bulb, socket or
both.
NO
Replace the tail/
brake light.
7-30
LIGHTING SYSTEM
3. 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
Negative tester probe → black
• Set the main switch to "ON".
• Start the engine.
• Measure the voltage (AC 12 V) of blue
on the tail/brake light coupler (wire harness
side).
• Is the voltage within specification?
YES
This circuit is OK.
ELEC
NO
Replace the rectifier/
regulator.