Yamaha YBR 125 Service Manual page 209

Inspection of signal system
1.No function of the horn
1.Horn switch
Remove the branch-connector of handle bar
switch(left)from the bundle conductor
Check if the switch between the Pink and the
Black.
2.Voltage
Connect min·multitester(DC20V) to guide
wire of horn
Positive guide wire of multitester→Brown guide
wire
Negative guide wire of multitester→Frame ground
Turn the main switch to "ON".
Check the voltage at the binding post of horn brwon
guide wire gets to 12V.
3.Horn
Connect the min·multitester(DC20V)to "Pink"
binding post of horn.
Positive guide wire of multitester→Pink guide wire
Negative guide wire of multitester→Frame ground
Turn the main switch to "ON"
Check if the "Pink"guide wire voltage at the
binding post of horn gets to 12V.
Adjust or replace horn
Meet normal value (12V)
No function of the horn
Signal system
Abnoraml
The horn switch is failure,the lever switch (left)
should be replaced.
Out of normal value
If there is poor layout from the main switch
to the horn binding post,repair is needed.
Out of normal value
If the horn is failure,replace it.
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ELEC