Here's an easy one....

[markjs]

My headlight hasn't worked since I got my bike.. The speedometer illumination lights are also ht or miss. I just jumped a hot wire to the light for a while, but after riding a lot the light started to work like it should, but then started quitting again.

The guy at my local bike shop thinks it might be the starter cut out switch, but I can't remember for sure, but it seems to me the light never worked unless the engine was running which would mean that it is powered by the alternator. Does anyone know which it is?

Also, does anyone have any clue where the weakest link may be? I have cleaned nearly every electrical connector on the bike and made sure they are tight but for the life of me I have been unable to find the problem.

[79XS11F]

The head light on only when the engine is running is the correct situation. this however does not mean that it only draws it's current from the alt. Once the engine is running the whole system including the battery is interconnected. Otherwise you would be sh*t out of luck if your alt failed and it happened to be dark out.
Weakest link leading to hit and miss operation is bad grounds or breaks in the wiring where the harness goes into the head light pod.
With the bike running twist pull and push on the harness in the pod area and see if you can ether kill the head light, make it go on, make it brighter or dimmer.
Rob

[Jerry]

On my XJ the headlight is on when the ignition switch is on, bike running or not.

One way to troubleshoot is get yourself a 12v test light (around $4.00) or a cheap multi-meter ($10.00) and check for voltage at the headlight connector. One lead is ground, others are high and low beam power. Check for voltage between a good ground and the leads; 2 should have power (flip your high/low switch to make sure) and the 3rd is the ground. Intermitent problems are often tied to a bad or corroded grounding circuit. Could also be you need to clean the contacts in the high/low switch.

I have found that jumpers with alligator clips on each end are useful for troubleshooting, as you can use the jumpers to make temporary circuits. For example, use one to go directly to the negative battery terminal and use that circuit as a known good ground. Check for voltage between the jumper and the pins in the headlight connector.

Note: a broken headlight filament can cause intermittent problems. Examine the light closely to see if all looks OK.

[boyat68]

Don't forget that the XS1100s have a headlight relay that is held up by the ac generatorand is only on while that generator is running. There is a yellow lead directly from the generator
to the coil of that relay. There is a black lead running to ground off of the other end of that relay coil. This pulls down a contact that connects the red/yellow lead to the headlight fuse through
the main switch. If the headlight works intermittently, then it may be that the contacts of the headlight relay are malfunctioning. Short of taking the relay apart and burnishing the contacts, you would have to replace the relay. This is just another place to check.

[81xsproject]

I believe the relay trigger comes from the regulator, not the stator.

[mro]

All three white wires from the stator do go to the retifier/regulator.
One branches off before the reg/retifier and goes to the tach, this same wire also branches off agin, has an inline diode and goes to the head light relay.
If all the connector/plugs are good...leaves the relay and reserve lighting unit as main suspects.


mro

[jurgenkoppen]

mro is right

mro ,
I just used the info you provided to fix the headlight on my 80SG restore project.
(which is starting to look and sound great: I just scored the NOS muffler system on Ebay a few month ago)
You are right, that the white wire at the relay comes directly from the stator, mine did not have continuity to the relay, and so the relay did not click in.
I bridged over from from one of the white wires by the regulator to the relay, and voila, the headlight came on.
Now though, in writing about this victory over this electrical issue, I am stating to have doubts: you mention here a diode, and by bridging the cable I also bridged the diode.
I did not run the bike for long, just turned it over long enough to see if the light comes on, and it did. Is bridging the diode going to hurt my stator/regulator or the relay?
Do you know? If so I might just disconnect that bridge again and instead put in the on/off switch by bridging the wires over the relay....
Any insight is appreciated much.
Cheers, Jurgen

[thewiz]

Weakest link might be the fuse block .... ...

I had a similar situation but without the intermittent dash lights I think. Turned out that one leg of the headlight fuse holder on the fuse block had melted and loosened up causing h/l circuit to break contact at times. Was able to JB Weld the contact back in place and it's been fine since.

[mro]

Is bridging the diode going to hurt my stator/regulator or the relay?
I have no specs on the diode, but sure yamaha had a reason for it being there.
Most likely is to prevent any return current on that wire. It does come from an AC generator...


mro