Why would my headlight not work?

[Train]

Ok GS gurus, let's try this one: I'm down to very few issues with my rebuilt 91. Actually, just one issue - my headlight doesn't work. I've taken a voltmeter to the three prong connector and verified that there is no electricity going to it. The headlight wires come out of the main wiring harness. Neither the main harness nor the headlight or headlight assembly was damaged when the bike went down last fall. And yet here I am with no headlight.

So my question is this: what should I start investigating? I've got a voltmeter and can test whatever I need. I'm getting pretty good with wiring work (just wired in my new electronic tach/speedo, put new connectors on and rewired the left switch cluster from an 05 to work on my 91, etc.) so I'm not real worried about not knowing what I'm doing. But what should I start looking for? Keep in mind, aside from the break light not illuminating when the front break is depressed, everything else electronic works awesome on the bike (not really sure what's up with the front break not lighting up the rear break light, but one thing at a time).

Any thoughts at all on this one?

[The Buddha]

There is a yellow wire in the wiring harness. It goes from the ignition lock to the wiring harness I think.
That being disconnected = no headlight.
Yes I have had this same thing happen last year.
Cool.
Buddha.

[joshr08]

theres the diagram for you.

[Train]

Yes, okay, we're onto something here. I am using that diagram. Budhha, what yellow wire are you talking about? Can you highlight it on that diagram? I have a yellow wire that is going to the blue connector that used to give me my neutral light/oil light/etc (top left of the diagram). But I don't have that connector plugged into anything since I replaced my tach and speedo. Does that yellow wire need to be connected to the headlight yellow wire to close the connection or something?

Any help you guys can provide would be awesome - especially since you put that diagram up and that is exactly the one I've been using. I have to teach until pretty late tonight, but I'll be eagerly checking in throughout the day (but probably not responding) to see what you guys have to say.

Thanks for takign the time to help. I assume it is something silly like this (the yellow wire not closing a connection) because the headlight wires should be getting electricity and there is no damage to any of the obvious things that would create a problem there.

Thanks in advance!    Off to work! 

[The Buddha]

I'll try tonight ...
Cool.
Buddha.

[average]

I'll try tonight ...
Cool.
Buddha.

You're right,S. After I got my new headlight switch i forgot to hook up that wire and I didn't have a headlight. I believe the wire is actually yellow and green.

[Train]

Okay, I investigated the yellow and yellow/green wires. Neither have a current going through them when the key is turned to "on." Can you guys start telling me what wires I should check and report back about? I really think this issue will be quickly solved, I just don't know how the hell to solve it myself. 

[average]

Is the wire pluged up is the question? Someone posted the wiring diagram. Check it out and see whats up or you can just trace the wire from your lefthand switch and make sure that it's plugged in. Easy as pie. 

[Train]

Yeah, see, that's just it. From what I can tell, all of the wires are plugged in/connected properly. The switch cluster is from a 2005, though, and the rest of the bike is a 91.

The wiring diagram that is posted above is the same diagram I've been using in my garage as I worked through the wiring problems over the last few months. So I'm really familiar with it, and a bit confused why the headlight doesn't work.

I'll get back out there tonight and start messing around with stuff again, but can anyone help guide the process of tracking down the problem? There is probably an order-of-operations here that would make the most sense in diagnosing this problem, but I don't know what that order is.

[joshr08]

the white wire to the headlamp is low beam yellow is high beam hence the reason for the yellow going to headlight and high beam indicator on the dash.  You should have a yellow with a white tracer wire going to your switch on your handlebars.  do you have power there?

[The Buddha]

Didn't get time and daylight yesterday. Today aint looking too good either. Sorry train.
But what average said ... yea ... And its not a hot wire, I think its a relay type wire. So dont look for voltage, look for connectivity ... to what ... dunno.
Cool.
Buddha.

[werase643]

you have a wiring diagram
and a voltage meter

start at the battery where you know there is 12 volts
and trace the wires to the headlight check every connection (both sides)
when you don't have 12 volts through a connection or switch.....
you found it

[Train]

Ah ha, we got a working headlight. 

Turns out, some of you were right all along - the yellow/white wire wasn't connected. However, I maintain that a normal, non-electronically trained person would not have noticed this or thought it relevant because someone had taken those yellow/white wires (and there are two of them) and combined them into one wire, and then put a bullet type connector on the end.  So I just ahead and replaced that connector with a pin-type connector, plugged it back in, turned it on, and wouldn't you know it, power to the headlight. And as a bonus, the highbeam works, too.

Unfortunately, I couldn't find the screws to remount the headlight, so I just had to order those. Hopefully they will be here soon. Thanks, all, for your help!