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

[ratbyk]

Wire Diagram

Max, there is a link to a XS wiring diagram on the board right now.
Go to the thread "anyone got a wiring diagram' started by Nastydude. Part way down is a posting by Sidecar Kev. Click on his link and you will have your wiring diagram. If you cannot find it then send me a personal Email with your Email addy and I will send you one directly.
Ken/Sooke (Ratbyk)

[Shuriken]

Well, I was sick and tired of the headlight and tail light not working and the oil/brake light warning light coming on.

I spliced wires from the fusebox (signal circuit) to the tail light and from the fusebox (headlight circuit) to the headlight relay. I also put dielectric grease on all the connections.

Now I have a headlight and tail light so I could at least pass inspection in the future. While I was at it I also fixed my turn signals, too.

I noticed while driving today that the tail light/oil warning light comes on and off intermittently, apparently to various engine vibration, etc.

It was easier for me to hack into the circuit than trace down a crappy connection. My headlight now comes on when I turn on the ignition switch....

So my new question is, how does the tail / oil warning light even come on? It seems to me it only comes on when there is NO voltage to the tail light or some voltage from the oil sensor, so what logic component in the circuit knows when there is no voltage?

What I am trying to figure out is exactly what condition causes the warning light to come on (lack of voltage to the tail light or voltage from the oil pressure sensor?) so that I can isolate a circuit to fix this intermittent problem. There has to be a component (switch, relay, ....) or some component that sends voltage to the warning bulb. If I know how the warning bulb is turned on I can go find the component doing it and check the circuit going to and from that component.

Is dielectric grease a conductor?

Ben

[ratbyk]

Idiot Light

Ben, dielectric grease is a conductor.
I do not know what controls the oil pressure idiot light on a special, (thought they had a low oil level switch) but on my 78E standard the low pressure idiot light is controlled by a sending unit located of top of the crankcase directly below the carbs. Power goes to the oil light as soon as the key is turned on. It passes from the light down to to this sender. If there is no oil pressure or it is low then this switch will ground out allowing the light to come on. As long as it has pressure it holds the contacts apart so that the light won't come on. (no ground for the power wire coming down from the light) This is the best I can do in understanding how this circuit functions.
I believe the low oil level sender for a special is located on the crankcase under the bike. Don't own one so can't check.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[Shuriken]

Thanks for that info on the oil pressure switch. That is clear, now I need to know how the light would come on with a tail light failure....

Ben

[TopCatGr58]

Hey Ben,

A quick check of the wiring diagram shows that the same ground wire splits into a "Y", one goes to the oil pressure "grounding" unit switch, the other goes into something called the
"Light Checker Unit". The power lead comes from the RESERVE Lighting unit! So....apparently there is a switch in there that causes the light to go to ground when the tail light circuit isn't working(brake Light out!?).

And of course, if that wire coming from the warning light is worn anywhere against the frame, then it will come on when that worn spot contacts/grounds out against the frame!
Happy troubleshooting!
T.C.

[Shuriken]

Thanks TC.

I don't have the diagram in front of me at this computer but...

It sounds to me like there should be a specified voltage on a wire going to the reserve lighting device. So if I can figure out which color of wire that should be (blue/black?) and trace that wire everywhere it goes, I should find a short somewhere. Unless it's a simple quick connector fault somewhere, I should expect to rip the wiring harness open to check along the blue/black wire or whatever it is...

A worn spot on the insulator should explain the intermittence. Now I wonder why my neutral light no longer works?

And on another side note, how hot is the headlight glass supposed to get on this bike? It seems to run a bit warm....

Ben

[Shuriken]

I also looked up dielectric grease out of curiosity, and found this.

[randy]

Ae7f,

As for dielectric grease, it is NOT conductive. If you want to increase the conductivity at the connectors, use a conductive grease. it's actually an emulsion of powdered copper in petroleum grease. Does two jobs. Keeps moisture out and helps reduce resistance at the connectiion.

Randy

[ratbyk]

Dielectric Grease

Sorry for the misinformation guys. I was always under the impression that conducting current "WAS" the purpose of dielectric grease. I guess moisture shielding and heat conducting is it's main purpose.
Ken/Sooke

[Shuriken]

I think a whole connector must be wacky. Tach jumps, now neutral light does not indicate, ect., etc......

I hate electrical problems the most....

On the 79sf, were the front turn signals supposed to act also as running lights when the key turns on?

Ben

[TopCatGr58]

Well, according to the Clymers,

The 78-79 Standards were both running and turn signals, but the Special wasn't.
T.C.

[ratbyk]

Electrical Sickness

ae7f, From your description of a variety of electrical all in the same area I would suggest you go straight to the grounds. Every time a group of circuits start to act up it usually is a common ground for that group.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRar"

[Shuriken]

That wouldn't surprise me. It's really hard to find everything. On the left side of the bike under the battery tray there is a ground I cleaned up. My battery terminals are very good. I'm sure there are a bunch more... I'll have to get out the diagram and just look for where the grounds fuse in to the main frame ground circuit.

Ben