Yamaha XT660R S Service Manual page 424

EAS00797
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. Brake light switches
• Check the brake light switches for continu-
ity.
Refer to "CHECKING THE SWITCHES".
• Is the brake light switch OK?
YES
NO
Replace the tail/
brake light bulb,
socket or both.
NO
Replace the brake
light switch.
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SIGNALING SYSTEM
3. Voltage
• Connect the pocket tester (DC 20 V) to the
tail/brake light coupler (wire harness end)
as shown.
Positive tester probe → yellow 1
Negative tester probe → black 2
• Set the main switch to "ON".
• Pull in the brake lever or push down on the
brake pedal.
• Measure the voltage (DC 12 V) of yellow
1 at the tail/brake light coupler (wire har-
ness end).
• Is the voltage within specification?
This circuit is OK.
8 - 41
ELEC
2
B B
L
L/R
Y Y
1
YES
The wiring
from the main switch
to the tail/brake light
coupler is faulty and
must be repaired.
– +
NO
circuit