'79sf - Oil Pressure / Tail Light Bulb - Help

[Shuriken]

I'm dealing with electrical gremlins again, this time in my '79sf.

I searched for a good wiring diagram for this model and didn't find one.

The Oil Pressure / Tail Light indicator bulb comes on. I know the tail light has no voltage to it because I tested for it with the multitester. The brake light works and my turn signals work, but I have no tail light, headlight, or guage lights. I tested for voltage to the headlight and to the tail light and found none.

I don't like "combination" idiot lights. I don't like the idea that the oil warning light is on the same circuit as a running light. I can deal with a faulty tail light but obviously don't want to run a bike with an oil failure.

Has anyone else lost the headlight/tail light on this model?
Any suggestions to what I should check besides just connectors?
Anybody have a wiring diagram for this model?

Thanks,
Ben

[Shuriken]

Nevermind about an SF wiring diagram - have/found one. But advice on what to check for headlight/tail light failure would be good.

[Winterhawk]

Maybe the fuse box?

[Shuriken]

Thanks. I did check that. Tested out okay.

In fact, today I just tried to check voltage on just about any of the hot wires. Battery measures 12 volts but I'm getting funky voltages on some wires .... 4 volts here, 6 volts here, .01 volt here.....

Worse, I don't know what the wire codes mean. On 9-16 of my factory manual, the flowchart says "check for battery voltage on "L/B" wire to reserve unit. What color?

Then it says check voltage on "L/Y" wire. I would think these were light blue, light yellow... something like that but I think L here is supposed to be something else.

I don't know what L stands for in LY, LB, or LG.

Where is the headlight relay located at on these bikes?

Ben

[Ken Talbot]

The color code legend in my Yamaha manual lists the following:

L/W Blue/White
R/L Red/Blue
L/Y Blue/Yellow
L/G Blue/Green

Not intuitive at all!

HTH...

[TopCatGr58]

Hey Ben,

You and Materi have the same year/model bike. I have a Clymer's with COLOR diagrams, and will scan it and post a link to it for you both.

Hey Ken, once you figure the code, it really is kind of intuitive, since "B" is probably already reserved for BLACK, and blue starts with B, they used the next letter in the spelling "L" instead!?

One note, so far the diagram seems to show an error for the neutral light switch, having it connected to one of the red/white power leads for the pickup coils instead of the light blue wire that is part of that group of wires that DOES go to the neutral light, and it's shown going to that wire in the 80-81 diagram!?
T.C.

[TopCatGr58]

79SF Color Wiring Diagram

Hey there Ben,

Here's that Color Diagram for the 79SF, hope it helps vs. your black and white one!?
79SF Color Wiring Diagram
T.C.

PS.: It's at 200 DPI, Appx. 8" x 10" to allow you to be able to read it. You should be able to print it to full page and have it relatively legible, but you can size it to your liking!

[Shuriken]

Thanks. I'll let you know what I find.

Ben

[JohnSg]

Excellent wiring diagram! Saved for future reference. Thanks TC.

[Shuriken]

Okay:

The other night I checked out all the connectors. Most of them crumbled as I tried to remove them. On the others, I ground off the locking tabs with a dremel.

Anyway, I cleaned the corrosion off of all of the connectors as much as I could. Used steel wool, a file, and the dremel. Also cleaned the fusebox terminals.

Good news is that all of my lights work now except the headlight. I have front and rear turn signals, tail, and brake light. The oil pressure/brake light indicator works as it should, now. Neutral light works too, as well as turn signal indicator light.

Only thing that does not work is the headlight. No operation. I'm suspecting the headlight dimmer relay.

What do you guys think? I'll have more time to check today - it got dark on me last night.

Ben

[Ken Talbot]

Hey, Ben, if you want to really do it right, you can get replacement parts for those connectors from Cycle Recycle They sell the brass terminals as well as the plastic blocks.

[Shuriken]

SUWEEET.

I didn't know about those....

I'll have to see if there is enough variety to redo them all. I think I'll still have a problem with the connectors for the TCI unit.

If I were able to replace most of the connectors, I could clean all of the contacts REALLY good, since the wires would be exposed.

Ben

[Ken Talbot]

With the cleaning you have already done, did you figure out how to use a jewellers screwdriver inside the plastic block to release the lock tabs so you could pull each terminal out for a thorough cleaning? Of course, with new terminals, and in nice new blocks, you wouldn't have to do any cleaning!

[Shuriken]

I could get the new connectors but don't know if I have the time/money to put into the bike. I had all the lights working after I cleaned the terminals. Fired her up and took it around the block and the brake warning light came on again and my tail light stopped working again. Same problems as before. Obviously crappy connections somewhere still.

Since this problem came back and the headlight will not work, I'm toying with the idea of an engine swap. An engine swap would also allow me to really polish up the engine and paint the frame.

Can you tell I hate electrical problems?

Ben

[TonimusMaximus]

Hey TC. How can I go about getting a color diagram for my 78E?