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Tail light works. Brake light doesn't...

29K views 27 replies 12 participants last post by  buschchris1 
#1 · (Edited)
I just bought an 86' VT700C and it runs great. However, the brake light doesn't work. I'm sure the brake light switch is just fine, as the indicator on my dash lights up whenever I depress either the front or the back brake. The only issue is that the brake light in the rear does nothing.

I tried switching the bulb expecting that it could be that one of the filaments that is bum, but both filaments were just fine and the brand new bulb worked the same.

I was wondering if anybody might have a suggestion on how to fix this? The only theory I have come up with, is that there is a blown fuse and for some reason this locks the brake light either always on, or always off (the tail light seems unusually bright to me, but I could be wrong)?

Thanks!
-Nico
 
#2 ·
Get your wiring diagrams and check for shorted or open wires running from the switches to the light. Also Disconnect the wires for both of the switches and make sure they do open and close as you operate the brake. Check the socket and make sure the contacts aren't bent, broken, or otherwise damaged or dirty...

Are both filaments always on or just one of the two?
 
#4 ·
My schematic is for an 88 but the colors should be the same. Green wire is ground. Green/Yellow is switched +12 and us common to both switches. There will be a disconnect probably under the seat and it's a safe bet a bullet connector is loose or pulled out there. The only other disconnects are for the switches themselves and they are probably good since you are getting an indicator at the gauge.
 
#5 ·
First question - is your taillight lit at all without the brake? They use the same ground.

If no lights, you have a bad ground.

If normal taillight / no brake light, you have a bad feed to the brake light.

If always bright, you have constant brake light and either a short between tail & brake or a bad brake switch, etc.

Once we can break it down to one of these three paths, we can narrow our scope pretty quickly.
 
#7 ·
Check the Brake light 12V feed...
The wire probably has an open curcuit between the switches and brakelight somewhere...

Unfamiliar with yours...

Merry Christmas & Good Luck on this diagnosis
Ann & Dennis
I had to run a wire to get the rear brake to turn on the brakelight on my 98 model :D
 
#8 ·
I have the same bike...shes in my signature below, Jezebel. You have a blown tail light fuse...this is indicated by the tail light indicator lamp on the instrument cluster being lit.

With your bike on the center stand or kick stand, turn your handlebars all the way to the right as if you were riding. Look directly under the Left Side near the Triple Tree/Neck...you should see a small 1-1/2" x 3" or so plastic cover...it is held in place by 2 Phillip-headed screws. Take the screws out and pull the cover...it can be a slight pain in the rear. Tour tail light fuse should be the 5th down from the top..it is 10 amp blade fuse...replace it.

If you replace the fuse, the dash indicator lamp should go out. If it blows again, look for a shorted wire somewhere...trace from the tail light back...

See attached image below...
 
#10 ·
Thank you for all of your help guys! Keep in mind, I'm brand new to owning and working on bikes, so please bear with me as I try to figure this out.

I was able to change out the fuse for the brake light, and it made no difference. I bought a smart fuse and it does not indicate that it has blown either. So the fuse is good, and I've started looking into the wiring now. Currently I'm trying to figure out how to expose the line for my inspection from the tail light to the brakes. First, what is the easiest way to remove the front seat? Also, which connections should I be focusing on, and where can I find them on the bike? I have a copy of the 86-87 service manual, which includes the wiring diagrams, so I can look at those, but I can't promise I'll understand it all the first time.

Thank you again guys, I really appreciate all of the help!
 
#12 ·
Thank you for all of your help guys! Keep in mind, I'm brand new to owning and working on bikes, so please bear with me as I try to figure this out.

I was able to change out the fuse for the brake light,
Ok, lets start right here...I cut the rest of your quoted post because this may be where your problem is. So lets clarify for a second.

Is the Tail Light Indicator on the instrument cluster on, and do you have brake lights when you either squeeze the front brake lever or press the rear brake pedal? If you have brake lights, then by all means the brake light fuse you checked is good. Did you check the Tail Light fuse as well? Was it good?

If you go back and look at the fuse panel and cover picture I posted, you will see that the Brake is also joined by Turn & Horn. If all 3 of these items are working, your fuse there is indeed good. If you have no Tail Light, it is usually 1 of 2 items, either the 10amp fuse is blown, or the filament on the tail light/brake light bulb is burned out. Please recheck the fuse panel...pull that 10amp fuse marked METER TAIL...I would almost bet a hole in a donut that that fuse is blown....
 
#11 ·
While checking connections, be sure to tighten up any loose bullets...
The service manual is a very important tool...
Follow the instructions and you`ll get the job done...


Merry Christmas,
Ann & Dennis


Welcome to the forums :D
 
#13 ·
I do not trust my eye sight when checking fuses. I always use a multi-meter to check the fuses to see if they have a open circuit. I also put the positive lead in the fuse block and ground the negative lead too check for voltage and amps in the block. Make sure you have power.
 
#14 ·
Years ago I spent hours troubleshooting a very odd automotive problem in which a spade-type fuse had an ever so tiny 'fault line' in the filament. It was not quite open, not quite a full connection. It was a resistor of sorts. Forehead slapper. I've used an ohm meter from then on.
 
#18 ·
I have been able to determine that both filaments on the tail light are in fact burning constantly without either of the brakes being depressed.

Or a maladjusted switch, stuck switch, or like was said, pinched wire.
 
#20 · (Edited)
Ruled out since the dummy light *only* lights when either lever is activated. If a switch were always on, the dummy light would also be always on.
Forgot about that. Yep. Gotta be a pinch or touching bullets.
Sometimes those wires inside the socket get mishandled and their insulation becomes receded, exposing the conductors. Then they can twist a little, cross and touch.
 
#21 ·
Ok. Seems we are all now in agreement...you will need to start checking wiring and connections. Taking the front seat off will help, so here how to do this.

1) Take the passenger seat off if you have one. This is done by using the ignition key...and the Helmet Lock on the right side rear under the passenger seat bottom. Insert the key and turn clockwise I believe to release the lock mechanism for the rear seat...it can be a bit sticky.

2) Once the rear seat is off, looking straight down the back of the drivers rear seat edge, you should see (2) two flange nuts sticking up in front of the plastic storage compartment..these are 10mm heads...remove them. Now the rear of the seat will lift clear of the bolt ends, then pull rearward and the front portion of the seat will come free of the factory hold down in rear of the fuel tank.

I have attached 2 images below...1 is Helmet Lock/Passenger Seat Release and the other is a pic of where the driver seat slips under the rear section of the fuel tank/frame. Unfortunately, I dont have a good picture of Jezebels seat off and rear fender shown...

http://s5.postimg.cc/x1hmk4z0n/Mini_Storage_3_Mounted.jpg
http://s5.postimg.cc/503l6ftqf/Modified_Tank_Bib_with_Cell_Phone_Window.jpg
 
#22 ·
Hands on experience is best ;)
Especially with knowledge of the Bike in question & Pics :D

Good Luck on this issue...

You`re in good hands here...

Merry Christmas,
Ann & Dennis

LLLL, bring it over, the lift is empty :D
 
#23 · (Edited)
After lots of exploring with a voltmeter and exploring every inch of wire even remotely related to the brakes and brake light. Not a single problem with any of it. Naturally, I didn't trust my assessment, so I ended up calling a guy who runs a nomadic repair business (a super helpful and generous man), and after coming up with the same conclusions about the wiring, he discovered that whoever had last replaced the housing for the tail light had installed the light socket in such a way that it caused the brake light to always be on.

I guess sometimes the right answers really are hiding in plain sight! haha

Anyways, he fixed the problem in less than a minute, and was on his way.

P.S. thank you all for your help. You guys really helped me explore my bike in a way that would have been impossible otherwise.
 
#24 ·
When someone posts a fault on here most of us think that it is because something has gone wrong, we have no chance of finding the fault if it has always been there since installation.. glad you got the fault sorted out and very glad that you got to know your bike a bit better.. Before you do any future work on your bike take clear photographs of everything you undo and label them to show what they are..they will be very helpful when you reassemble your bike..

John.
 
#25 ·
If both filiments are burning your brake light is always on try adjusting the switch for the rear brake
 
#26 ·
I know a day late and a dollar short
 
#27 ·
Ok so 4 years later here comes me. Hope you get this and soon. I was wondering what the fix was. Something about the wiring to the tail light. Was it at the twilight housing or further back along the wiring? I'm having the same issue and I checked the things mentioned. Just stays on. Probably a bad switch but wanted to know what your fix was. Thanks.
 
#28 ·
Ok well I figured it out so oif anyone reads this despite the age of the Origional post then maybe it helps someone. So I took a 5mph dip and all though nothing serious the rear break pedal got bent in. Everything still worked. Well I replaced it and due to the new pedal haviing a slight difference in its range of motion the rear break light switch and spring were not releases back enough to trip the break light back to normal brightness. There is an adjustment screw on the bottom of the rear break pedal arm that you can tighten and that fixed it. Super easy. I attached picks. Sorry if the orientation is wrong but it should matter. First one is the spring that connects the rewar break pedal to the switch. It pulls as you break. The second is of the adjustment screw that I had to tighten all the way for it to allow enough give to release the switch. A lot like how old car break pedals work. Thank the steel horse gods it was something easy. Cheers.
 

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