Brake activates headlight

[thebottle]

I was bleeding the brakes today and I noticed that with the key is in the off position the headlight and dummy panel turn on when you press down on the rear brake. It doesn't do it when you press down on the front brake though. Is that normal? Everything else works fine, so I am thinking it might be normal but I have never seen that before and I recently had the bike torn apart so I might have mixed something up but I really don't think that I did.

[MrFreeze5]

I put a new brake light on after putting everything back together and now when I was bleeding the brakes today I noticed that when the key is in the off position the headlight and dummy panel turn on when you press down on the rear brake. It doesn't do it when you press down on the front brake though. Is that normal? Everything else works fine, so I am thinking it might be normal but I have never seen that before.

Sounds like youve got a 2 wires crossing and getting really friendly with each other. Id start by checking all your wires for fraying or exposed wires or shorts.

[thebottle]

Dang, I was hoping that I wasn't going to hear that... I guess the hunt begins. Lol.

[MrFreeze5]

Dang, I was hoping that I wasn't going to hear that... I guess the hunt begins. Lol.

I find a few odd things about this. I know the XS has an old electrical system, and i dont have my XS running at the moment, but here is what stands out as odd to me.

First, youre getting voltage through the system when the key is off. If the key is off, nothing should light up.

Second, the brake switch is actuating the headlights and idiot lights right? Those should be on seperate circuits to begin with.

Third, how would the wiring from the rear brake switch get crossed and activate the lights up front?

The only thing I could think of, and this is just off the top of my head, that would affect several light circuits at once is if they somehow have battery voltage running to them, but the ground is open somewhere along with a crossed wire, and the brake switch is closing the ground. just a guess though trying to incoporate everything. but yeah, check your wires well.

[thebottle]

Thanks for the advice.... what you said makes sense. I am going to look at it in a few days and I will report what I find out.

[fredintoon]

I was bleeding the brakes today and I noticed that with the key is in the off position the headlight and dummy panel turn on when you press down on the rear brake. It doesn't do it when you press down on the front brake though. Is that normal? Everything else works fine, so I am thinking it might be normal but I have never seen that before and I recently had the bike torn apart so I might have mixed something up but I really don't think that I did.

Hi bottle,
no, that is not normal.
The red line from the main fuse goes directly to the ignition switch. With the key off, nothing should be powered up at all.
What's supposed to happen is this:-
With the key on, running lights, horn & signals will work.
Also the coils are powered up and the starter will crank when the button is pushed.
Once the engine starts the headlight and the gauge lights will come on automatically.
BTW the tach will not work unless the alternator is working.
Did your bike always do this or only after you worked on it?
If so, it's most likely something you did, eh?

[thebottle]

Hi bottle,
no, that is not normal.
The red line from the main fuse goes directly to the ignition switch. With the key off, nothing should be powered up at all.
What's supposed to happen is this:-
With the key on, running lights, horn & signals will work.
Also the coils are powered up and the starter will crank when the button is pushed.
Once the engine starts the headlight and the gauge lights will come on automatically.
BTW the tach will not work unless the alternator is working.
Did your bike always do this or only after you worked on it?
If so, it's most likely something you did, eh?

Yeah, I crossed something that I shouldn't have so I will have to figure that out. One thing with what you said though... shouldn't the headlight come on right away when you turn the key on? You said that it only comes on after you start the bike, but I know that even before I tore it apart that it came on with the key. The PO messed with the wiring a lot so let me know if you made a mistake or not because I want everything to work the way that it was meant to work.

[fredintoon]

Yeah, I crossed something that I shouldn't have so I will have to figure that out. One thing with what you said though... shouldn't the headlight come on right away when you turn the key on? You said that it only comes on after you start the bike, but I know that even before I tore it apart that it came on with the key. The PO messed with the wiring a lot so let me know if you made a mistake or not because I want everything to work the way that it was meant to work.

Hi bottle,
yes, the headlight & gauge lights should only come on when the alternator is working. Presumably it's to save enough amps to work the ignition while the starter is cranking.
There's a white wire from the reg/rect that powers a relay via a diode. The relay turns the headlight and gauge lights on. The relay is a little brick of a thing with a black, a white, a red/yellow and a blue/black wire going to it via a 4-way plug. I disremember exactly where that relay is located but at least you can see it. The diode is in a clear plastic tube that's buried inside the main wiring harness wrapping somewhere under the tank.
That's how it left the factory, anyway. As you say, the dreaded PO has been messing with it so you are in for some wiring forensics.
FWIW, I reckon the stock wiring is over-complicated with mystery modules doing things that are not needful. My BSA only needs 7 wires fer chrissake (well, OK, 10 if you want signals).

[thebottle]

Well I looked at it today and figured it out. It was silly.

I have the front master cylinder off the bike and so the front brake switch is on because the lever isn't holding it down. When I held that down so that it was off then everything acted as normal. Apparently if you press both the front brake and the rear brake with the key off then it is supposed to turn the dummy lights and headlight on. Everything is sorted now.

The front headlight does come on with the key. I see that the PO took a tan wire and wired it in with the green one on the headlight. I am going to leave it because all my other bikes headlights came on with the key.