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Discussion Starter · #1 · (Edited)
hi everyone, i noticed that my brake light was out, but upon closer inspection i see this. it its so faint it's almost not lit at all, but only certain leds, the rest is out, it has a pulse/flicker. front brake lever and foot brake doesn't change. all the other lights (front park light, front headlight, all turn signals and license plate light) are still working. i wanna troubleshoot but i read there are a few things i found:

1) bad front brake switch
2) bad rear brake switch
3) bad tail light

questions:
1) is it likely that both brake switches gone bad together?
2) how can i test the tail light switch, i have a multimeter, but i dont know why 2 leads out of 3 do i hook into.
3) how do you test the brake switches?

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Welcome to the forum jgc731,

The first thing I would do it check if the rear light has a good negative connection (to frame).
Is the problem only for the brake light or does it concern the regular taillight LED's as well?
What year is your bike?
Testing lever switches or pressure sensors:
Disconnect the lead connector, set the multimeter to Ohms connect the multimeter leads to the switch/sensor leads and operate the switch/sensor.
There should be no reading when released and full reading when activated.

1) not likely that both switches fail at the same time but not impossible
 

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Discussion Starter · #3 ·
my bike is a 2016 duke 390 abs (usa). i cant tell if the tail light itself is dead or if it is actually a wiring problem that i need to track down and fix.

tested front lever:
i removed the 2 wires going to the front lever swtich. i put the multimeter leads on the two prongs (sticking out of the switch). the reading was 0.00 with brake lever activated and 0.00 while released.

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does that mean the switch is bad and needs replacing? is there a fuse i can check? how do i test the switch for the rear foot brake switch?

i tested the voltage of my battery and it read 13.51v.

i bench tested the tail lamp with a 12v battery that i use with a cordless drill and the right side of the tail light looked the same as in my original post which tells me that there is some power going to the tail light assembly.
 

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If you set the multimeter to Ohms, connect the 2 multimeter wires to the 2 connectors, shown in your pic and it reads 0 Ohm in either engaged and released position, this switch doesn't work.
The rear brake pressure switch is basically the same.
Disconnect the connector that comes from the pressure sensor on top of the rear brake MC and perform the same with your multimeter.
You press the foot brake to activate the sensor.
I'm not sure you are able to test the tail light this way but when you apply 12V to the backlight and only 2 out of all the LED's light up, it pretty much seems to me that the light is not working as should either.
For the fuse of the taillight check the manual.
I have no experience with USA bikes.

Just to repeat my remark in my first reply; check if the negative to the frame is connected firmly and works.
 
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