Weird problem: Brake light no workee

[baz666]

The tail light works, the signal lights work but not the brake light.
I've checked the bulb and changed it, yes, the double fillament type.
I've checked the wiring connections, all solid, all read well on the multi-meter. But when I press the brake pedal or pull on the front brake lever, nothing, no brake light.
I did notice a single brown wire with a female brass connector coming from under the gauge but there's no obvious place to connect it.
Any ideas at all would be much appreciated.
thanks,
baz

[Steve]

Skip the meter, use a test light.

Pull the bulb, check the contact for the brake light. If it lights, the power side is OK.

With the bulb in place, put the point of the test light probe on the socket on the side of the bulb, squeeze the brake lever.
If the test light comes on, you have a bad ground.

.

[baz666]

Sorry, I should have mentioned the bike is a 1983 GS750ESD.

I'm not sure what you mean by touching the point of the test light to the side of the socket with the bulb in place. With the bulb in place, there is a rubber housing around the socket which makes it impossible to touch the pointer anywhere on the side of the socket.

When I touch the test light to each contact on the spring loaded based plate, and thouch the other wire of the test light to the frame, each of the contacts light up.
So I'm guessing you're right, that there's a bad ground.

So should I try attaching the ground wire of the tail light/brake light wiring harness to the frame or the battery ground or is it better to remove the entire socket assembly and see if the ground is disconnected behind it.

If so, how in tarnation do I get to it inside the tail section? Do I have to undo all those screws and bolts on the underside?

[Steve]

Sorry, I should have mentioned the bike is a 1983 GS750ESD.

This is why we often suggest that you add this to your signature. It will show up with every post and you won't have to remember to do it.


One more quick test to verify a bad ground:
With the key ON, does the tail light come ON?
With the tail light ON and you activate either brake switch, does the tail light go OFF?
If so, it's a bad ground.

Start by following the ground path. Many bikes have three wires going to the light housing, one for tail, one for brake, one for ground. (The light housing is rubber-mounted, so they don't rely on a ground through the mounts.) Make sure that the ground wire has a good connection (you can separate the connector and use your test light there). If your test light comes ON there, your connection at the light socket must be good, so make sure the other end of the wire is connected properly to a ground.

.

[baz666]

Hi Steve,
Thanks so much for all your help.
With the ignition on, the tail light comes on. It stays on and doesn't change when I apply either the front or rear brake. And the brake light doesn't come on.
There are four wires coming out of the tail light/brake light harness.
White, Gray, Brown and Black with White stripe.

There are two wires coming from the rear brake.
Orange with green stripe and White

The same two colored wires come from the front brake.

I assume the white wire is the brake light and the orange with green stripe is the power wire.

I'm wondering if the ground is badly connected behind the socket. But I'm not sure how to get at it without taking apart the entire rear end of the bike, which is kind of hassle.

Thanks for any advice.
baz

[Skateguy50]

Could it be something simple like a bad connection in the socket?

It has two wires going in the bottom, one is for the running light the other for the brake light. Well different coils in the same bulb but still the wires at the bottom might not be connected well.

If you have enough slack on the wire sometimes you can feed it through the back and get the wire and metal cap to come out of the socket, I did that with mine and it was a loos connection. I stripped a little wire, soldered it and pulled it back through.

This is just my little experience with my 650 and might not even apply... just saying start with the basics. With bulbs I start with the bulb itself, look inside are both filament wires good or did one burn out? If good check the wires connecting to the socket, keep working away from the problem area till you find the issue.

[tejasmud]

Orange with green stripe is power, correct, it comes from the fuse box. It feeds the brake light switches, turn signal relay, then it turns into a gray wire in the harness that feeds the dash illumination bulbs and if there is a license plate light, it also feeds the horns which are Black wires.

Brown wire is also power. The brown wire comes from the ignition switch and keeps the tail light on, and it also should have a bullet connector near the headlight, normally nothing is connected to it. An auxillary of some sort, and there is a black with white stripe wire (ground) with it. If the 83" 750 has running lights on the front turn signals the Brown wire also feeds power to those.

The Black with white stripe throughout the whole harness will be ground. For the tail light, if the light is on, the ground is okay. The brake light uses the same ground as the tail light, and the turn signal grounds are crimp spliced into the same gorund if you peel back the black tape of the harness. But, if you have a tail light, the ground is good.

The white wire. Once either of the brake switches are triggered it feeds the power to the bulb at the tail light. The switches are "normally open" meaning it connects when actuated.


Have you checked the fuse in the fuse box? Second fuse from the top IIRC. Orange with green stripe wire. 10A fuse.

Could be the problem.


Also, have you gone to BikeCliff's website and downloaded the 83' manual? It has the wiring harness schematic, which would be a great help for you.

http://members.dslextreme.com/users/bikecliff/

E

[baz666]

The Black with white stripe throughout the whole harness will be ground. For the tail light, if the light is on, the ground is okay.

Yes, the tailight is working.

The white wire. Once either of the brake switches are triggered it feeds the power to the bulb at the tail light. The switches are "normally open" meaning it connects when actuated.

When I put power to the white wire and the brown wire, both filaments in the tail light/brake light bulb light up.
But when I pull on the brake lever or press on the brake pedal, nothing.
I've tried a different rear brake switch, still nothing.

Have you checked the fuse in the fuse box? Second fuse from the top IIRC. Orange with green stripe wire. 10A fuse.

Yep, the fuse is fine.

So it must be a connection at the back of the socket, as someone has suggested.
Great - but how do I get to the socket? Do I have to remove the entire tail section?


thanks,
baz

[tejasmud]

When I put power to the white wire and the brown wire, both filaments in the tail light/brake light bulb light up.

Sounds like the tail light is working. So, no need to disassemble the tail section. Unless you just really want to. I just put the tail section back on my bike so I'm familiar with what it takes and can explain. But, don't see the need if the filaments both work when power is connected to the wires under the seat.

I assume you are putting power to the white and brown wires under the seat, left side, and just behind the battery next to the inner fender. Correct?



If so, put these connectors back together with the harness, and try putting power to the white wires coming from either switch. If the filaments light up you are good from the switch to the tail light.

Have you checked to see if you have power at the switches on the Orange w/green stripe wires?

If there is power at the switch from the Orange w/green trace wires, and putting power to the white wires lights the filaments in the tail light the problem is the switches.


If there is no power before the switches then check to see if you have power coming from the fuse box. If you have dash lights and the horns work there is power coming from the fuse box.

Also check the power, Orange w/green trace wire at the turn signal relay it is located on the right side under the side panel. If the turn signals work you have power this far.

Any power there?



E

[Imreallycrazy]

Never mind, Someone already mentioned my thought.

[BassCliff]

Hi Mr. baz666,

When your "tail" light is on, is only one filament lit? Or are both lit?

The reason I ask is that after putting together my bike after my latest crash I noticed the brake light wasn't working. It turned out that the brake light was on all the time. This was because the contact pad on the front brake switch had dislocated during reassembly and was making contact all the time. After putting the contact pin back in the proper slot and reassembling the switch all was well.


Thank you for your indulgence,

BassCliff

[baz666]

Sounds like the tail light is working. So, no need to disassemble the tail section. Unless you just really want to. I just put the tail section back on my bike so I'm familiar with what it takes and can explain. But, don't see the need if the filaments both work when power is connected to the wires under the seat.

I assume you are putting power to the white and brown wires under the seat, left side, and just behind the battery next to the inner fender. Correct?



If so, put these connectors back together with the harness, and try putting power to the white wires coming from either switch. If the filaments light up you are good from the switch to the tail light.

Have you checked to see if you have power at the switches on the Orange w/green stripe wires?

If there is power at the switch from the Orange w/green trace wires, and putting power to the white wires lights the filaments in the tail light the problem is the switches.


If there is no power before the switches then check to see if you have power coming from the fuse box. If you have dash lights and the horns work there is power coming from the fuse box.

Also check the power, Orange w/green trace wire at the turn signal relay it is located on the right side under the side panel. If the turn signals work you have power this far.

Any power there?



E

Yup, everything works and there is power from every wire.
The signals work, the horn works, the dash lights work, the tail light works, the license plate light works. The test light lights up at the white wire and the brown wire and the gray wire where the tail/brake light connector meets the harness. There is power at the white wire and the orange w/green stripe wire just above the brake pedal switch. There is power where the front brake lever switch meets the harness under the gas tank.
And yes, there is power at both filaments of the tail/brake light socket when I touch the test light to them.
There is also power at the test terminals on the fuse box.
I also hooked up a spare rear brake switch I have and that doesn't work either so it's not the switch.
I can't for the life of me figure this out.
Is it something weird like the kick stand has to be up for the brake light to work? Seems ridiculous but this point, I'm grasping at straws.
thanks for everyone's input.
baz

[baz666]

Hi Mr. baz666,

When your "tail" light is on, is only one filament lit? Or are both lit?

The reason I ask is that after putting together my bike after my latest crash I noticed the brake light wasn't working. It turned out that the brake light was on all the time. This was because the contact pad on the front brake switch had dislocated during reassembly and was making contact all the time. After putting the contact pin back in the proper slot and reassembling the switch all was well.


Thank you for your indulgence,

BassCliff

You know, Cliff, I think both tail light filaments might be lit when the tail-light is on. I have to check to make sure but I did notice that when I was testing the tail/brake light connection to the harness.
So the contact pad is touched by the brake lever itself?

thanks,
baz

[Calvin Blackmore]

have you checked the rear switch for binding?

if its a tube type of switch they gum up and bind

if both filaments are on its a place to look

[baz666]

Yeah, I hooked up a spare rear switch and it didn't make any difference.
So I'm thinking Cliff might be right about the front brake switch keeping both tail and brake light filaments on. I have to check in a few minutes down in the garage that this is indeed the case. I'll post my findings.
thanks to everyone for their feedback and help. This is one incredible forum.
thanks again,
baz