77 gs 550 tail light problem

[johnhend]

I was installing a new tail light and I think I shorted something out. Now there is no power to the light. Front and rear Turn signals have power. Ignition works, headlights work. Just no power to rear tail light or stop light. Any idea of what to check. I don't think I've got a fuse panel anywhere.

[KitKat]

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

check his site and find your wiring diagram

[Nessism]

All GS bikes have a fuse box as far as I know. Have another look.

[KitKat]

the 300 doesn't only got an inline

[johnhend]

I think the problem is a loose wire in the ignition switch. Came back out to check it again after looking at wiring diagram and it worked fine.

[Redman]

Joe,

I think you have a double edged problem
- if problem happened and then cleared up, it is going to happen again.
- but, yet, cant fix it now while it aint broke.

Wiggle things one at a time and see what makes the light go out.
Yah, you are trying to break it again, ... so you can fix it, ... so it doesnt happen again.

Tail light AND brake light, you say.

(looking at 850G schematic for fuse and wire color info, same I think)
Brake light is the white wire from the brake switches. Powered by the 2nd fuse (org/grn wire).
Tail light is the brown wire from the ignition switch, in on position is also powered by the signal fuse (org/grn).
Tail light is the brown wire from the ignition switch (same), but when switch in the Park position is powered by the main fuse (red wire).

Since you say both the tail and brake light go out, then no need to suspect problem with the white wire (specific to brake light) or the brown wire (specific to tail light). We are looking for a problem in something that is common to both the tail and the brake light.

Wiggle wires till tail light goes out, concentrate on the org/grn wire all through out the bike, take off tank so can find it in more places, is more connectors in headligh shell also, take out headlight. Most importantly: Find the fuse panel (behind left side panel) and wiggle the signal fuse, wiggle the org/grn wire and follow the org/grn wire. Wiggle all connectors with org/grn wire till tail light goes out, then you have your suspect. As another test, when tail light goes out, turn key to Park and see if the light comes back on, then you know problem is in the org/grn wire.
If you wiggle all you can find of the org/grn wire and cant make the tail light go out. . . .

Then lets explore the other thing that is common to both the tai light and tha brake light, and that is the ground wire, the blk/wht wire back there. Wiggle that around till light goes out. Are a few of them back there, the one from the tail/brake light, and one for each turnsignal and licence plate light and such AND the one comming from the main wiring harness. Look for where the one from the tail/brake light connects to the one from the main wiring harness.

Also try your therory of the ignition swtich being the problem and try wiggling that around, and the connector on back of the switch. (I suspect not, or else you would problably have other problems also.)

Maybe pull head light fuse during all this so dont run down the battery.

Also: Other rule of troubleshooting, always suspect what ever you just did just prior. You say you just changed tail light. Hum.... look that over. Take it out and do again.

Tell us more what you find.

I figure you can wiggle things untill you find something to make the light go off and on, and then know that is where the problem is. If you get it to where light(s) go out but dont know what you did and cant get them back on ... well, that then requires a compley different trouble shooting techinque.

But when it is broke, then you can fix it, and then it works all the time.

You have a volt meter? or test lamp?

.

[Suzuki_Don]

The '77 GS550B has a single in-line fuse under the right hand side cover. But that does not seem to be your problem, otherwise nothing would be working at all if this fuse was blown.

[Redman]

The '77 GS550B has a single in-line fuse under the right hand side cover. But that does not seem to be your problem, otherwise nothing would be working at all if this fuse was blown.

Ew, Opps. I knew that late 70s and some early 80s two cyclinder bikes had only one main fuse.

Ew, and maybe ignition switch doesnt have a park position either.

How does the colors I mentioned above still line up?

I imagine that white is still the brake light, and brown is still the tail light, and problem is not either of those, since we are looking for something that would effect both the tail and the brake.

And ground is still blk/wht I would think.

.

[Suzuki_Don]

Yes REDMAN, the white is the stop light, brown the parking light and black/white is the earth. Could be an earth fault.

When I first got my bike the PO had the wiring back to front. The true earth from the frame (black/white ) went to the white wire and the white wire from the harness went to the black/white wire of the tail lamp. It still worked but everytime I pressed the brake pedal all the panel lights went off. Took me a while to work out what was wrong.

My Point: Make sure there is a good earth to everything in the tail light region. Follow that wiring diagram that you have printed out.