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Discussion Starter #1
I've done some investigating so far, but here's the gist:

I noticed one night my brake light wasn't coming on. Tail light works, I just noticed it didn't get brighter. Both front and rear are not lighting it up. So today I checked the connections and used a multimeter to do some test. The switches themselves have continuity. But there's no power running through the wires to the front switch (nor was there any power at the last connection to the tail light, which is redundant to say, but just noting). The fuse is good and I confirmed that power is running through the fuse box. So I checked the wiring diagram and it looks like there's multiple points I need to check. Only problem is, I saw where one of the wiring connectors is... behind the frame and in front of a cylinder, where it's going to be one hell of a time trying to get it out.

My main question here is does anyone know of any common points where connection is lost/corroded/etc.? So at least this struggle can be minimal.

The only thing I've done to the bike recently was a new rear tire. Other than that, it has been in hard rain more than usual. Even though it was under a cover, it was still wind driven into it more days than not.
 

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Discussion Starter #4
check the adjustment on your rear brake light switch thats what mine was and i had the same problem
See I haven't heard anything about that. It's currently threaded all the way out, does threading it in help? And wouldn't the rear switch not affect the front due to it splitting off the wire from the front to the tail light?

And yes the horn does work.
 

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Your rear brake switch/sensor could be "on" the whole time. If that is the case, you won't notice any change in brightness upon actuating either brake lever. Try threading the switch housing the other direction.
 

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Your rear brake switch/sensor could be "on" the whole time. If that is the case, you won't notice any change in brightness upon actuating either brake lever. Try threading the switch housing the other direction.
While I wish this were the case because it would be an easy fix, it can't be since I wasn't getting a voltage reading.
 

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Discussion Starter #7
Your rear brake switch/sensor could be "on" the whole time. If that is the case, you won't notice any change in brightness upon actuating either brake lever. Try threading the switch housing the other direction.
HOLY crap.... it was the rear switch staying on. So I'm just going to accept the lack of voltage when I did the multimeter test and be happy that my brake lights are flashing again. THANK YOU!

I am however confused on how the tail lights had 12v running to them but the brake lights had none, especially since the switch was stuck ON. Nonetheless... accepting it, unless anyone has any input...

Btw... this was thanks to my eagerness to get my bike back on the road after the rear tire slid out from under me on a cold winter day when it hit the white paint line in a turn. I just haven't noticed the brake light not working since then... which is sad. Good thing I always keep an eye on cars behind me eh?

Thanks again guys/gals for your input, if it weren't for this I'd probably be struggling with the harness connections.
 

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Mine did that (and is doing it right now as a matter of fact) after I adjusted the brake lever - I will actually be adjusting it today. I was able to track it down by pushing up on the spring that goes to the rear brake light switch which then turned the brake light off.
 

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HOLY crap.... it was the rear switch staying on. So I'm just going to accept the lack of voltage when I did the multimeter test and be happy that my brake lights are flashing again. THANK YOU!

I am however confused on how the tail lights had 12v running to them but the brake lights had none, especially since the switch was stuck ON. Nonetheless... accepting it, unless anyone has any input...

Btw... this was thanks to my eagerness to get my bike back on the road after the rear tire slid out from under me on a cold winter day when it hit the white paint line in a turn. I just haven't noticed the brake light not working since then... which is sad. Good thing I always keep an eye on cars behind me eh?

Thanks again guys/gals for your input, if it weren't for this I'd probably be struggling with the harness connections.
I'm glad it worked out. I don't know the wiring diagram too well, but it could be that the two areas you were probing were at the same voltage or shorted, thus resulting in a 0V reading.
 

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I noticed that my brake lights weren't being activated when I step on brakes. Squeezing the hand brake does activate the brake lights. A quick google & read of this post lead me to rotate the rear brake switch a few turns. Problem solved! Thanks.

P.S. Now on to replacing the fork oil & seals.
 

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guys, a couple of clarifying questions, because I think I ran into the same issue now:
1) if the brake light stays on all the time, does it mean that the switch thingy should come down in the bracket? I think that's right, given that pressing the lever pulls on the switch...
2) what's the best way to go about it? do I need to dismantle the whole thing or is there an easy way to adjust its position without messing up with the actual brake system? It's tight quarters there and I can't really see how it's held in place.
 

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Thx @sv650bklyn !

I moved that thing all the way down, and up, and no luck. All LEDs in the back are on, at what looks like full power. Not sure where to look next. Could it be a faulty switch? All other lights work fine, so I don't think it would be a fuse or something like that.
 

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Did you check the switch on the front brake lever?
I just did. It seemed fine on the first look: clicking, and moving in/out as I use the front brake lever. Then I pulled off the plastic connector and I checked the resistance through the switch with a multimeter. It was OL (over-limit, so high) with the brake off, and ~200Ohm with the brake on. I though that's too much and so I sprayed some WD-40 into the switch the best I could and then I pumped it for a few minutes. I got the resistance to show 3-4 Ohm in the ON position after a while.

That still didn't fix the issue and so I did the same treatment to the rear brake switch: WD-40 and pumping. Didn't do anything. I'm not sure where/how I can check if the rear switch is good. There is no connector on it, and I'm not sure where the other end of the wire is, that goes up from the switch and behind the frame.

Any help will be appreciated.

FYI: bike has been parked outside for the last 5 years of its life. It's under a good cover, but it does get moist underneath from condensation. I do ride in the rain when the situation calls for it. I don't see much corrosion on it, but who knows what's going on inside those little switches... Everything else works perfect though.
 
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