Brake light problem

[deo]

I have spent hours looking for a solution to the problem of my brake lights staying on. I have traced the wiring harness for a bad connection, pulled the bulbs and checked the seats on the bulbs, checked fluid levels, checked brakes themselves but I still can't figure out where the problem is coming from. I even went so far as to check the schematic in the book to trace out the wiring.

Brakes work great! The only issue I have is the lights stay on full all the time and the tail lights don't come on at all.

deo

[TopCatGr58]

Hey there Deo,

If the brake lights are staying on, then it's possibly not a matter of a bad connection, but of the brake light switches being activated. There's one on the foot brake, and one on the handlebar brake. Unplug them both and the brake lights should go out, and the running lights should be burning. Then plug one switch in at a time and see if the lights come on. If they come on when you plug one of the switches in, then you've probably found the bad switch!? You should be able to take it from there!
T.C.

[deo]

Topcat,

Just went out and tried that. no go. I have already replaced the rear brake switch and so I just disconnected the front one and no difference in the lights. The front one is connected to brown wires and not white/blue and black. couldn't see the black one at all.

deo

[Czekus21]

Originally posted by deo
Topcat,

Just went out and tried that. no go. I have already replaced the rear brake switch and so I just disconnected the front one and no difference in the lights. The front one is connected to brown wires and not white/blue and black. couldn't see the black one at all.

deo

There is a wire that runs from the rear brake light switch to the peddle. You may try adjusting that a little bit longer. I'll bet your brake light goes out

[deo]

Thanks, I actually took it completely off so that there wasn't any tension on it and it stayed on. I have a thought that it might be a grounding problem somewhere on the bike. When I ran a test light on the black wire that attaches to the ground it lights up. when I disconnected it at the connector under the seat the side that goes to the lights illuminates the tester and the side going towards the switch doesn't.

I hate electrical problems. I pulled all the wires, blue/white, the yellow and the black off the back tail lights and then reconnected them one by one. The brake light always comes back on and the tail lights never do. This happened one day while riding down the road so it can't be something badly rewired but should be something that is due to wear and tear of some sort. Or it should be as TC said the switches. But both of them test out good.

Has anyone ever had their back taillight housing go bad? Does anyone have another tail light housing or a suggestion on how to check it out.

deo

[ratbyk]

Sure sounds like a grounding problem to me. The ground wire for the tail light is not grounding. Power for the tail light is going out through the brake light bulb/element. This leaves the brake light on all the time but no tail light.
Don't know about XJ's but on my XS there is a ground wire for the tail light on the under side of the rear fender. It can get corroded
and stop grounding.
Ken/Sooke

[Parr8hed]

this may sound stupid and obvious, but I had that problem recently and the front brake lever was not impacting the front brake switch. A little adjustment and the light went off. I think that would have showed up if you had it disconected though.

[deo]

I am going to look at the grounding issue again but think that the black wire is the ground and it is on a clip on top of the lighting assemlby.

Is there any kind of out of the box solution that would be a duh if we discovered it. I have to go for inspection or can't ride the bike next month so I really want to get this fixed.

Other wise the cars think I am a bike rider that rides his brakes. lol

deo

[randy]

Deo,

This may sound dumb, but are you sure you're not confusing the running light with the brake light?

What I mean to say is, maybe your light that's on all the time is your running light and your brake light isn't coming on?

If that's the case, I'd go with the grounding problem.

[TopCatGr58]

Hey Deo,

Like Randy said, could be bulbs in backwards, but doubt that if they were working right, and then went bonkers! Okay, just reviewed the wiring diagram for the XJ's brakes!

The brown wires at the rear and front switches are HOT, from the fuse block, then they go to the computer via a common tap....a Green/Yellow wire which apparently is the triggering wire for the computer.....which then sends the power out to the brake light and tail light via the yellow/white and blue/white wires...but I don't know which is which!? The BLACK wire is just the common ground that both filaments share.

So...the computer controls power to the brake lights. The handlebar and foot switches control or send the signals to the computer. So, with the switches pulled off, there shouldn't be any power going to the Green/Yellow wire to activate the brake lights. So...either the brown and green/yellow wires have gotten worn together so that they are making contact, and therefore "shorting" sending power to the Green/Yellow wire and to the computer to turn ON the brakes, OR... the computer may be faulty? And I think the computer may be turning OFF the tail lights when the brake lights are on to conserve power/amperage, I've seen many cars to the same thing!!

So I figure somehow power is being sent to the Green/Yellow wire when it's not supposed to....you may need to trace that wire thru the loom looking for worn contact areas, but I think it's either the switches, or the wires very close to the switches!
T.C.

[deo]

TC,

What you have said makes sense only that the black wire at the tail lights is hot. I haven't heard of a common ground ever getting juice to make it hot. So there has to be a short somewhere that is sending juice to the common, or is my electric 101 all screwed up and it is supposed to be hot at times. You tell me, cause I don't know.

The logic of the yellow/white and blue/white is good I suppose that I should trace them further than I have. I traced them from the junction next to the TCI, which by the way is the place where the black is no longer hot going back to the rest of the bike, hmm.

Still stumped but I sure am learning a lot about the bike.

deo

[John]

If the black wire isn't grounded properly, the it will be hot until it is grounded.

[deo]

Go Nationals,
Oh sorry John, thanks for the advice. I think that the issue may be the bolts that ground the tail light housing could be corroded. I am going to wd 40 them and see if I can tighten them up. They do serve as the ground for the lights don't they?

deo

[TopCatGr58]

Deo,
The black will be hot as long as there is a hot signal coming to the light socket from either the Blue/white or Yellow/white wires. If you pull the bulbs out of the sockets, you'll probably find that the black wire is NO LONGER HOT, cause the bulb isn't completing the circuit to the ground wire!!! However, if it is still hot, then you've probably got a faulty bulb socket(s)!?

If you're going to trace wires, you should check the Green/Yellow ones from the switches. The brown ones are hot, and the green/yellow ones shouldn't be until the brake levers are actuated, which causes the switches to jump the brown to the G/Y which then sends the signal to the computer, which then sends it to the Blue/White or Yellow/White to the brake lights!
Keep at it!!
T.C.

[John]

I believe the bolts do provide the ground. Nothing on these bikes is case grounded. Everything has a groundwire. Use a jumper wire from the ground wire to a good ground on the frame, or even the battery. That should help. If the light is working but just bass ackwards, then I don't think the ground is the problem. Yo say the ground goes cold near the ignition module? You may have a broken ground wire. That would explain the ground wire being hot up to that point in the harness. I wish I was there to help, because it sounds like it's something really simple, and were just making too much out of it. I like a good electrical challege. I don't know much about electronics (that's Randy's gig) but the electrical system on these bikes is fairly simple. Especially the tail/brake lights.
Good luck with it.