Topic: SOMEONE please HELP.. Going nuts over a simple question

[sawyerds]

I have one, hopefully simple question that I really would love to have answered.  I'm not sure why no one seems to want to answer it.. If I have broken forum etiquette, just let me know..  I have obviously searched and tested extensively.  Maybe there is something wrong with my search but..

talking about a 1976 CB750 F

WHY does the BROWN/WHITE  (aux light & signal running light) wire go into the left control, specifically the HL control portion?? 

I have gathered wiring diagrams, cross reffed them, etc.  My bike seems to be wired completely stock.. (99%sure)

I understand that the left control does have an input brown/white wire to power the running lights (3-filament stock bulbs, LT.BLU/WHT & ORNG/WHT from control to front signals)   But WHY does it go into the HI/LO HEADLIGHT portion of the switch (according to all '76 F diagrams) when the BLK/YELLOW provides this power!  This makes no sense to me, other than as a backup should your HL fuse blow while riding at night..  even still, I test for continuity on the switch wires only,  between the BRN/WHT  and headlight wires (DARK BLU, WHITE, BLK/YEL) and get none.. but all the diagrams say it provides pwr to HL control too.  Also, if this were the case, wouldnt the headlight would remain on when the start button is pressed?!  PLEASE HELP!!

Thanks a ton in advance to whomever wants to assist me!!

[bimly]

I think the headlight goes off on start due to current draw rather than circuitry.

[LesterPiglet]

I think the headlight goes off on start due to current draw rather than circuitry.

I'm not up to speed with 750 wiring or US spec wiring but I believe the headlight is switched off when the starter switch is pushed.

[MCRider]

I think the headlight goes off on start due to current draw rather than circuitry.

This won't answer anything directly. But its my understanding that the headlight actually switches off when the starter is engaged. This is to defeat the "always on" circuit of later model bikes and route maximum power to the starter.  Same for cars.

Its not just an act of dimming due to current draw, which wouldn't accomplish anything positive relating to starting the vehicle.

I think.

PS: I was writing mine while LEsterPiglet was posting.

[sawyerds]

Hey thanks guys for taking the time.

The question definitely still remains though.  Baffles me that no one seems to ever wonder about this or mention it! How do so many people rewire bikes or change switches and ignore this!? There must be an issue with my search. I have tried every type and search strategy. Nothing.

But Yes, I understand the right side momentary starter switch.  Yes, it turns off the otherwise  'always on' headlight to devote load to the starter. Simple. The headlight is the always on portion and the starter the momentary.

Again, I'm asking WHY BRN/WHT AUX LIGHT PWR HAS ANYTHING to do with the HEADLIGHT CONTROL CIRCUIT. Pls refer 1976 CB750F SUPER SPORT  (Attached) @ bottom left area....Though this also appears to be a common wiring for other models as well.

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[jorwesflow]

Br/W is for the Taillight and gauge illuminators. But I can't figure out why it breaks off and runs to the left hand control module. Maybe it's left over from earlier years when there was an actual ON/OFF switch for the headlight? Did that ON/OFF switch turn off the taillight too?

[jorwesflow]

See attached 1976 CB550F wiring addendum

[Don R]

 Does the brn/wh power the switch and the right hand start switch breaks the ground to turn off the headlight?

[goldarrow]

brown/white needs to be connected to left hand control HL switch to work properly if your right hand control doesn't have headlight on/off switch.  now i just need to go find a starter button and the internal assemblies so i can do push start

your left hand control HL switch is 3 wires internally, open it up and peek in it, you'll see brown/red (if i remembered correctly)

[sawyerds]

WHY WOULD THE BROWN/WHITE WIRE NEED TO BE CONNECTED TO THE HEADLIGHT CONTROL SWITCH.   

The above statement... This is my question.  Again, I REALLY appreciate the replies, but I understand what color wire is labeled for what; I have looked at wiring diagrams, hence me posting one specific to MY bike.  The above question is what I would like to have answered. If my question is unclear, (I may be too wrapped up in my problem),  then just tell me and maybe I can be more specific. 

Treat this as a US model bike complete with stock wiring.  NOT really a question pertaining to a trouble shooting problem with my own bike.

To DON R:  no, as you can see from the diagram, these are both power feeds with their own fuse, which apart from my question should seem to be completely independant!

TO GOLDARROW:   Please explain your reply.  Why would the BRN/WHT connect to the headlight regardless of anything?

And to clarify...  The brown/white DOES need to enter the left bar control housing, in order to provide power for the RUNNING light portion of the turn signals (between TURN SIG PORTION of the control-through the lt blue/white stripe and orng/wht stripe to the RUNNING LIGHT FILAMENTS. (This is necessary because the GREY is an intermittent power feed fed from the flasher, to provide blinking signals.

BUT WHY THE HL CONTROL!!??

[goldarrow]

your headlight needs common power when you turn on Ignition key, and that brown/white came out of ignition key.  so, when you have headlight at Hi beam and you get power, switch to Low beam, you get power.  when you push start, the whole system of dash lights and headlight pauses momentarily, so that the starting motor spins with good juice from battery. (don't remember if Blue or White wire is Hi beam or Low beam). 

what does the headlight on/off switch do on earlier bikes controls? turn off headlight, tail light and clock lights.  so, put it all together that's how i interpret it from reading the diagrams.

hope this helps??? 

[ANDY W]

that wiring diagram has some errors. it has the white wire from the low beam side of the head light going to the left hand turn switch and the blue wire coming out of the low beam switch going to the left turn lights

[Jerry Rxman Griffin aka MuthaF'er]

Without delving deeply into this I can tell you from experience that after getting the entire bike wired up there were 2 unmatched wires leftover and 'stuff', perhaps turn signals??, that did not work. There is supposed to be a jumper wire to connect these two unmatched wires that made EVERYTHING work correctly. I'm thinking this occurs in the junction box at the downtubes. This does NOT show up on any wiring schematics that I've seen. Don't know if this will be any help but it was MY mystery. 

[martin99]

I'm a total idiot when it comes to wiring but just a thought...

Some European countries demand that front and rear lights are always on - think Volvo. Would that wire have something to do with cutting the power to the rear light, as well as front, on start?

[TwoTired]

The Br/W wire goes to the turn signal portion of the switch group, as it powers the front running lamps.

The lamps are turned off during blink selection so the signals go from bright to dark, rather than bright to dim.  This makes signaling more pronounced and a bit more likely to be noticed.

The Br/W wire has nothing to do with the headlight on the 76 model.  Headlight interruption during starter button activity is performed in the RIGHT control group.

[sawyerds]

Thanks two tired. That confirms my thoughts exactly. (or the way it actually works) .  I guess I'm just flipping out over an incorrect diagram? Because, as I said previously, there is no continuity btween brn/wht and  HL power regardless of hi or Lo selection. ...so is it incorrect? There are other more obvious mistakes in the diagram as well, like the lo HL and orange signal wire being swapped

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[TwoTired]

What manual are you using?  I much prefer the Honda shop manual.  Clymer can be ok,  But I only expect them to be a generic guide, for general models.

[sawyerds]

I have been using the one I posted above several posts ago, and then I have the electronic version of the 'Honda Service Repair Manual' available on this site in the moto manuals post.  I'm not sure but I think that's the same manual as the Honda shop manual?  Also I have to refer to the '76 F supplement diagram which is a little grainy.

It does clearly show a USED connection of the TL wire in the left control, among the headlight selection control wires.  Used as power in addition to the black/yellow, and then selecting either Drk Blue or White for HI/LO respectively. 

Just cant figure out the purpose of it there.. seems detrimental if anything, connecting two fused circuit's power leads that should be completely separate after leaving the main bus to their fuses..?

[lucky]

You are trying to do two things at the same time. that is why you are having such a hard time.

You can understand WHY the wiring is the way it is OR....Just put the wires where the wiring diagram shows them.


Trying to do both is the problem.
BTW.....This is not a simple question .It is many many questions. Why is that way? Why do they do that, that way? etc.,.


Just wire the bike like the diagram shows you.

[sawyerds]

The bike is wired the way that it shows me.  I will be changing it (lets not worry about that or how or why for now).  So yes, i want to understand WHY, simply.  If it is indeed that complicated, I am honestly want to know all the more.  It could teach me a new concept.. and hey this here is the perfect forum to do so, right?

I just ask that anyone who still wishes to contribute, read at least some of the above and look at the places in the diagram I am referring to.  I understand that many of you that have and will reply, know this bike like the back of your hand.  Still, my question looks like its a seldom asked one, though closely related to others.  so bring on the theory..

[lucky]

Sometimes to really understand a switch you need to take it apart so that you can see HOW the mechanical design of it is. Then you can understand why there are certain wires in it.


The wiring diagram usually just shows the wires going into the switch, but it does not show you how they connect and are switched.

[sawyerds]

Well ok... I do plan to take the switch apart to find the answer myself when I get time this weekend. 

But the part in question is that the tail light wire (brown/white).

It feeds into the left bar control, and I understand why...(to power the front RUNNING lights independently.  In opposition to a selected blinker, and also while in the neutral blinker switch setting, to power both running lights on, separate from the rear (and with constant pwr, unlike the gray intermittent pwr from flasher).

SO..  I can't believe I'm saying this again but, what business (whatsoever) does it have being connected to the HEADLIGHT circuit within the left bar control.  I'm talking about the HL switch here, the actual switch that involves the black/yellow (HL fused power), blue (high beam), and white (low beam).

I guess I'm explaining this poorly but that's as plain as I can put it. Just ask if you have questions about what I'm asking! I'm new to bikes as you know, but I  know what I need answered.

Thanks again for your time.. Hopefully I can get somewhere with this. I thought it would be a simpler question to ask, and answer.

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[CB750F2]

OK. The Br/W wire gets its 12v from the Tail Light fuse and it is connected to TL1 on the turn signal switch. Some diagrams show that TL1 and HL are bridged at all times. I believe that this is not the case. If you have a look at the wiring diagram for the CB750A in the Clymer manual you will see that there is no connection between HL an TL1.
The purpose of the Br/W wire is to provide power to the tail light via the ignition switch when in the RUN position, provide power to the running lights when the Turn Signal Switch is in the neutral position and to illuminate the tacho and speedo.
You should be able to confirm the above with a multi-meter. Pat

[KRONUS0100]

i also have the 76 750F.  i totally rebuilt the harness my way with relays.  headlight is on seperate circuit with seperate on/off switch.  i vaguely remember that brown white wire at the HL portion.  i believe it actually supplies the 12 volts to the headlight. when i did the rewire, i also removed the headlight off feature from the starter button, hence the seperate on/off switch.
  according to the diagram, the brown/white splits going into the lefthand control.  part goes to headlight and part goes to turn signal.


scratch all that.  that brown/white wire goes to the taillight and marker lights.  supposed to provide the power to them when ignition is turned on.  the turn signal portion is there because of the marker lights..   hope that helps.

[sawyerds]

Thanks guys,

Yes it this helps.  It helps by confirming everything I've said in the above posts. So I gather the verdict is that all these multiple diagrams are just plain wrong.  That's what everyone seems to be leaning towards, and I have also tested this by testing continuity between HL components and the TL wire. (with the switch off the bike- switch side wires only).

I guess the short of it is... Error in the diagrams. Whew.. that was intense.

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