Brake light always on - 1979 GS850

[Steve]

OK, Cowboyup saw something in your latest pictures that might change things a bit, and this probably confirms it.

Just did... and same result. Grounded the wire to the bike, and plugged it into the black (ground) wire in the white connector. Then, plugged another wire into the battery and the other end into the brown (both bulbs dimly lit, but only one filament on the brake light) and then the white (only the license plate light brightly on).

The license light should not change birghtness, it should only be ON or OFF.

What Cowboyup noticed was some "iffy" wiring. Please disconnect ALL the hwiring at the back of the bike, it's not really all that much. There should be the 3-pin connector to the tail light, a gray wire that feeds the license light and four bullet connectors to the turn signals. Please make sure they are ALL disconnected so there is NO electrical path from the front of the bike to those lights.

Repeat the two wires into the 3-pin connector test. If your license light changes brightness, there is something wrong in that assembly, unless there is some "customized" wiring between the white connector and the bulbs.

If you go to BassCliff's site, (bookmark it, you will be using it a LOT) you can get a very nice copy of a color wiring diagram for an 850. It's not quite the right one for your bike, but it has the easiest-to-follow colored wires. The difference between that '80 diagram and your '79 bike are the igntion (points vs electronic) and the turn signal controller (different style, different wires feeding the controller). Other than those items, that is a very good diagram to follow. Click HERE to get the diagram for your '79.

I have a sneaking suspicion that there are some wires crossed in there, it will be easiest to just pull them all and start from scratch.

.

[natejelovich]

Please disconnect ALL the hwiring at the back of the bike, it's not really all that much. There should be the 3-pin connector to the tail light, a gray wire that feeds the license light and four bullet connectors to the turn signals. Please make sure they are ALL disconnected so there is NO electrical path from the front of the bike to those lights.

Repeat the two wires into the 3-pin connector test. If your license light changes brightness, there is something wrong in that assembly, unless there is some "customized" wiring between the white connector and the bulbs.

OK, did this (disconnected all connections to the tail light) and did the test. Results: no lights came on...

So, I removed all wires from the tail light unit, did the test, and none of the lights (license or tail/brake) came on. Is that normal?

If you go to BassCliff's site, (bookmark it, you will be using it a LOT) you can get a very nice copy of a color wiring diagram for an 850. It's not quite the right one for your bike, but it has the easiest-to-follow colored wires. The difference between that '80 diagram and your '79 bike are the igntion (points vs electronic) and the turn signal controller (different style, different wires feeding the controller). Other than those items, that is a very good diagram to follow. Click HERE to get the diagram for your '79.

I have a sneaking suspicion that there are some wires crossed in there, it will be easiest to just pull them all and start from scratch.

.

Yes, BassCliff's site has been awesome! I've checked out the wire diagrams before (a bit like hieroglyphs to me before all of this but with your help I think I'm understand it more.). Looking at the diagram and my bike, everything looks correct...

Gray wire: connects to license light
White wire: connects to tail/brake light
Brown wire: connects to tail/brake light



Anything I'm missing?

[Steve]

OK, did this (disconnected all connections to the tail light) and did the test. Results: no lights came on...

So, I removed all wires from the tail light unit, did the test, and none of the lights (license or tail/brake) came on. Is that normal?

OK, you disconnected all the connections, then used your two test wires to connect the battery to the light, and got nothing?

The only two reasons I can see for that happening would be 1) a dead battery and 2) your tail light assembly is messed up. Since you have seen the lights come on rather recently, I don't think it's #2.

I've checked out the wire diagrams before (a bit like hieroglyphs to me before all of this but with your help I think I'm understand it more.).

Yes, it looks like a big tangled mess of spaghetti, but it's not all that hard. The only wires you need to be concerned about at this time are the black, white and brown wires that go to the tail light assembly. Yeah, the gray one to the license light is there, too, but it has its own connector. If you look in the middle of the right side of the diagram, you will see the light and the wires. The black bar that goes across the three wires is your white connector, so you can stop looking there and only worry about what is to the right of that connector.

Looking at the diagram and my bike, everything looks correct...

Gray wire: connects to license light
White wire: connects to tail/brake light
Brown wire: connects to tail/brake light



Anything I'm missing?

Just running the test wires from the (charged) battery to those wires that are in your fingers. At the first of your last post, you said that you got nothing, I find that very strange.

Oh, while the white and brown wires do go to the tail/brake light, you need to know that the brown one is specifically for the tail light and the white one is for the brake light.

With ALL the wires disconnected from the bike and your test wires connected to the black and brown wires, your license light should not light, but the tail light should.

.

[natejelovich]

Just running the test wires from the (charged) battery to those wires that are in your fingers. At the first of your last post, you said that you got nothing, I find that very strange.

Oh, while the white and brown wires do go to the tail/brake light, you need to know that the brown one is specifically for the tail light and the white one is for the brake light.

With ALL the wires disconnected from the bike and your test wires connected to the black and brown wires, your license light should not light, but the tail light should.

.

OK, now I am really confused... I retried the test and it worked. I unplugged all of the wires (including license plate light) and re-hooked up the two wire test. Touched the brown, tail light came on. Touched the white, brake light came on (brightly).

Before I did that, I checked to make sure the bike would engage (and it did) to ensure the battery was charged. I also removed the bulb and put it back in. I also made sure the ground on the chassis was on well.

I don't know what changed exactly, but when I did the test, it worked (meaning, the lights came on as they were supposed to). I tested quite a few times to make sure and it seems like it's fine...

But, I plugged the white connector in to the other side again, tested the brake switches, and still nothing... So, after all of that, back to square one.

Next test?

[cowboyup3371]

If you plugged the connector back in then something is wrong there. Start peeling off the tape from both sides and check your wiring.

[natejelovich]

If you plugged the connector back in then something is wrong there. Start peeling off the tape from both sides and check your wiring.

Could the problem be anywhere else or do you think it's just at the connector?

[cowboyup3371]

You need to pull tape back from both sides (taillight and harness) and check for yourself. Did you take a power test light and hold it against the harness end of your connector to check for power on the brown and white wires? If so, and you got power there, then it's on the taillight side.

BTW, take a picture of that connector plugged in please. Do the wires line up properly?

[Steve]

OK, now I am really confused... I retried the test and it worked. I unplugged all of the wires (including license plate light) and re-hooked up the two wire test. Touched the brown, tail light came on. Touched the white, brake light came on (brightly).

Sounds GREAT!!

That tells you that the wiring, sockets and bulbs are all in good shape.

I don't know what changed exactly, but when I did the test, it worked (meaning, the lights came on as they were supposed to). I tested quite a few times to make sure and it seems like it's fine...

What changed is that you eliminated a BUNCH of "iffy" wiring connections and started from scratch with just ONE connection. That one happens to test "OK".

But, I plugged the white connector in to the other side again, tested the brake switches, and still nothing... So, after all of that, back to square one.

Next test?

Do you remember what I said back in post #19?

Testing in a systematic way will eliminate variables as you go. ... Once we see the results of those tests, we will move on to the next one.

Now that you know that the lights are working, we can work on what is feeding the lights.

Do you have a test light or a voltmeter? Either will work, but a test light is easier and quicker. Clip the ground wire for the test light to the battery negative or a good chassis ground. Put the point of the probe in the white connector's brown wire. Turn the ignition key ON, you should have power. If not, check your other lights to see if they are working. If they are, your fuse is OK, so the problem will be between the ignition key and the tail light.

.

[mrbill5491]

By this time I would have rewired the connections. I would have got out my test lite and match the wires to its corresponding lite function. Just like you would for a trailer connection.

[Steve]

Very true, mrbill, but not everybody is as savvy about taming all the mysterious smoke that travels through those wires.

.

[mrbill5491]

Very true, mrbill, but not everybody is as savvy about taming all the mysterious smoke that travels through those wires.

.

Guess I'm gifted But when it comes to painting my bike I'm I could use a volunteer, I have all the stuff ready lol.

[natejelovich]

So, I bought a volt circuit tester last night (http://www.harborfreight.com/circuit-tester-30779.html) and hoping to get some time to test the connectors. I don't even have all the right tools!!

Hopefully I can locate the problem...

[mrbill5491]

So, I bought a volt circuit tester last night (http://www.harborfreight.com/circuit-tester-30779.html) and hoping to get some time to test the connectors. I don't even have all the right tools!!

Hopefully I can locate the problem...

Now you be cooking....

[Steve]

That is a great tool.

There are times that you will need a voltmeter, too, but in this case, you really only need to know if you have power or not, so a light coming ON (or not) is really much quicker and easier. I probably use my test light much more often than my meter.

.

[natejelovich]

Do you have a test light or a voltmeter? Either will work, but a test light is easier and quicker. Clip the ground wire for the test light to the battery negative or a good chassis ground. Put the point of the probe in the white connector's brown wire. Turn the ignition key ON, you should have power. If not, check your other lights to see if they are working. If they are, your fuse is OK, so the problem will be between the ignition key and the tail light.

.

Ok... so tested the connector coming from the bike (not the tail light) and, not too surprisingly I guess, the tail light lit the test light up, and the brake (white) did not...



Just for kicks, I also tested the turn signal bullet connectors, and no power there:



Not sure if that means anything in this same situation or not, or if it's completely separate. Similar to the brake light though, it was working not too long ago, and, from no conceivable changes from me, no longer works...

I also tested the front brake connector at the front (near the headlight) and rear connectors and no power there either.

So... does this mean the next thing is just pulling the tape from the wires and re-wiring??