GS1100G(K) - No tail light - it's not the bulb - need your input

[MtnManCA]

Hello,

I just noticed that the tail light, the license plate light and the instrument illumination of my 1982 GS1100G(K) (fairing removed) don't work.

The tail light works when the key is in the "Parking" position.

I checked the tail light and license plate light bulb and they are OK.

I have to admit that I never checked these lights after removing the fairing more than a year ago. All other lights, including brake light work. I never ride in the dark which is one reason why I haven't checked/noticed this.

Here comes the part that is confusing to me: I removed the connector from the ignition switch to check which terminals get connected at different ignition switch positions.

Diagram.jpg

In the "Parking" position the red wire does get connected to the brown wire and the tail light is on as it should be.

In the "On" position, however, the gray wire gets connected to the brown wire and the orange wire gets connected to the red wire.

According to the wiring diagram the gray wire should get connected to the red wire and the orange wire to the brown one.

I hesitate changing the wires in the connectors, worrying that this may cause damage.

I am the third owner of the bike so changes to the wiring system may have been made that I am not aware of.

The bike starts and runs very well and the charging system works very well too.

Please let me know what you think I should do to fix this.

[MtnManCA]

The diagram of the ignition switch from the original post came from the Clymer manual.

I found a DIFFERENT/non-matching diagram in the Suzuki Shop Manual that matches what I saw on the bike:

GS1100GK SHop Maual Ign Sw.jpg

Sorry for the rotated view, wasn't able to correct it.

I will double-check all connections to figure this out.

[tom203]

This diagram from bass cliffs site might help. Previous owners can be devious

http://members.dslextreme.com/users/bikecliff/images/GS1100G_1982_wiring.jpg

[MtnManCA]

This diagram from bass cliffs site might help. Previous owners can be devious

http://members.dslextreme.com/users/...982_wiring.jpg

Thank you! This is for the GS1100G. Mine is the GK version which is slightly different from a wiring standpoint.

[MtnManCA]

I checked the voltage at the 3-wire connector for the tail light and brake light of the tail section of the bike (Black/White [ground], Brown, White) with the ignition switch in the "On" position.

Between the brown wire (tail light) and ground there is -50 mV (?) - what does this indicate?

With the ignition switch in the "Parking" position the tail light works just fine.

Any pointers at which other points to check?

I went through the entire bike and checked/cleaned all electrical connectors I was able to get to.

[TheAlt]

I checked the voltage at the 3-wire connector for the tail light and brake light of the tail section of the bike (Black/White [ground], Brown, White) with the ignition switch in the "On" position.

Between the brown wire (tail light) and ground there is -50 mV (?) - what does this indicate?

With the ignition switch in the "Parking" position the tail light works just fine.

Any pointers at which other points to check?

I went through the entire bike and checked/cleaned all electrical connectors I was able to get to.

I'm not sure if there is a separate ground for that circuit, but if you take a wire and ground the frame to the one of the bases of the Tail or Stop light does it illuminate?
I had a faulty ground (Honda) so I wired another ground to the chassis from one of the turn lights.

Alt

[phydeauxmutt]

Your description in the first two lines of post #1 and the picture in post #2 are correct.

It sounds like the gray wire is not being fed. It comes from a connector that might be under the tank. On some bikes, it might be in the headlight bucket, but on your GK, I would be confident saying it's under the tank, probably at the right, front corner. In the diagram that tom203 posted, you can see that connector at the top, just below the engine stop switch. WARNING. The colors of the wires going to the ignition switch are NOT correct.

From the LIGHTS fuse, power goes to that connector, where it gets split to feed an orange wire to the turn signal control unit, a yellow wire to the headlight dimmer selector and a gray wire to the gauge lights. The connector is the same one that has the infamous "headlight loop" for the stator wires. Check for power on the gray wire at that connector.

[Redman]

If the tail light lights with key in the park position, then know the problem is not the ground for the tail light etectera.

Seems like good information from Mr PDM above (but I havent studied what he said).

Let me describe about the same thing:

Find that grey wire and see if it has power. It gets its power from a jumper at a connector (connector on harness to the kill swtich, &start button) , the jumper is to the org/grn circuit which is the Signal Fuse (2nd).
DO you get things like the oil pressure light and gear indications? THose are also on the Signal Fuse org/grn circuit.
Do you have the tach and speedo face lights? THose are on the grey circuit.

THat brown wire for the tail light (tail light only, not plate light) comes from the ignition swtich. In On position the brown wire (tail light) is connected to the grey wire from the org/grn Signal fuse. In park position that brown wire (tail light) is powered by the main circuit. So if the tail light comes on in park position, then know the tail light ground must be okay, so the tail light ground is not the reason the tail light doesnt come on with key in ON position.

Note: The earlier editions of the Clymer manauls show the ignition switch wrong, well, the schematic wires are okay, its the little function chart that is wrong.
ON connects main to org to power the top 3 fuses (Head, Signal, Ignition), and connects gry to brn to power the tail light with signal power.
PARK only connects main to brown to power tail light (only) with main power. Doesnt do anything to power the Head, Signal nor Ignition.

[Redman]

I think Mr PDB and I are saying about the same thing. Except he calls it "Light" Fuse, and I call it "Signal" fuse.

The schematics dont label the fuses.

The fuse block on my 82 GK labels them as (top down) Head, Signal, Ignition, Main, Aux.
So that is what I wrote on my schematic.

[Redman]

I checked the voltage at the 3-wire connector for the tail light and brake light of the tail section of the bike (Black/White [ground], Brown, White) with the ignition switch in the "On" position.

Between the brown wire (tail light) and ground there is -50 mV (?) - what does this indicate?

With the ignition switch in the "Parking" position the tail light works just fine.

. . . . . . .

THat indicates one of two things:
Either there is no power there
OR
You are not using the meter properly.

Try measurting voltage there again with key in PARK position (which you said light works) and if meter reads close to battery voltage, then will know are using meter properly.

But, really, you already are using the tail light to tell if there is power on the brown circuit, since it lights with key in PARK position. So we know is power ther with key in PARK but not with key in ON. What we need to find out is why is ther not power there with key in ON position.

Now lets use meter to test the grey circuit. Maybe you can look up at bottom of the ignition switch to find the grey circuit and the brown circuit.
While you are there can also check meter operation by checking the red (main) and org (main back to head-signal-ignition) circuits.

.

[MtnManCA]

Thank you all for your input, very much appreciated!

It looks like the problem is solved.

I focused on the gray wire, checked also all other cable connections under the tank and found that the gray wire was connected to the wrong wire (White/Green) and two other wires were also wrongly connected by me when I eliminated a multi-cable plastic connector a few months ago. I must have been very absent-minded.

I triple-checked all connections and connected the wires the correct way. Turned on the ignition and now the tail light, license plate light and instrument lighting all work.

[phydeauxmutt]

Thanks for the follow-up.

It's hard to admit doing something wrong, hopefully everybody will learn from this.

[rphillips]

Mtnman you should be embarrassed, nobody else has ever done anything like that. Glad you got it sorted & let us know.