Topic: Headlight not working ?

[rddcw]

Can't get my headlight to operate ?  Headlight bulb working, tested right off battery.  My wiring plug that plugs into the back of the headlight is a little different in colors then what the wiring diagram shows. I have a "Blue" wire instead of Black as the wiring diagram indicates, but the other 2 colors ( white and green ) are the same. All the wires appear to go where they are supposed to go according to the wiring diagram.

When you turn on the ignition switch, the neutral light lights on the dash panel as does the front running lights. But when I operate the headlight switch ( on/off ) at the right handlebar control, nothing happens at the headlight ?

I opened up the handlebar switch and looked inside and can not see any broken wires or possibly any grounding out going inside if that's possible ?

I sprayed some Deoxit contact cleaner inside the opened switch contact area and operated the switch multiple times, but nothing changed ?

I even sprayed the Deoxit cleaner at all the wiring bullet connector after unplugging them, nothing still ?

Shouldn't I read Voltage at the headlight plug somewhere when the ignition key is on and the headlight switch operated in the on position as well ? With my Volt/Ohm meter I don't see any voltage ?

Any ideas or how to test to find where the problem is ?  Forgot to say that the Fuse is good too.

[ekpent]

 Blue wire is what I see on the Honda's not black. What year and model of bike ? Some of the later year models had a deal in the starter button that automatically cuts power to the headlight while starting that can malfunction. I have a 1976 CB750F that can get a little wonky there and cause the headlight to not work. More suggestions coming I am sure from others.

[TwoTired]

Flip the Hi Lo switch a few times to see if it is intermittent.

All I got til I know what bike were are dealing with.  Might be start button on later models.  It interrupts the head light power during start.  Until the switch body disintegrates.  Then the contacts wander about looking for action.

Cheers,

[rddcw]

It's a 74" CB 750 K4, sorry I forgot to mentioned that .

[rddcw]

Opened the left handlebar switch as well and sprayed some Deoxit on the inside contacts moving them back and forth, No Help 

[Don R]

  Swap out the fuses anyway and check the brass terminals for corrosion and looseness.  If you don't have spare fuses, you need some.

 I have a bike in the shop now that's intermittent when I wiggle the main fuse or stick a probe between it and the holder.

[rddcw]

I did try a different fuse and the brass fuse holder is tight. No Change ?

When I turn the ignition key on and the head light switch to on, shouldn't I have power ( voltage ) at the 3-prong head light socket ?  I don't measure any there ?

[ekpent]

 The 1974 model won't have the headlight interrupt in the starter button so scratch that idea off the list.

[evinrude7]

i'm thinking it's still in the hi/lo switch. 

[Yamahawk]

Break out your volt meter, and start at the beginning, test each section of the circuit for 12v. and trace it either from the headlight or to the headlight.
Charlie

[rddcw]

As I said earlier, I'm not getting any Voltage reading at the headlight 3-prong socket ?  I'll look at the wiring diagram and try to figure out where the voltage path goes ?

I'm assuming that I can take one of my probes from my volt/ohm meter and go to battery or chassis ground, then use the other probe and touch various contacts where the voltage path would going to the headlight ?

[evinrude7]

did you check the ground for the headlight? 

[HondaMan]

The 1974 model won't have the headlight interrupt in the starter button so scratch that idea off the list.

Actually, it does: the headlight interrupt first appeared during the 750K3 in 1973, mixed back-and-forth with an ON-OFF switch on the right side and the Hi/Lo on the left side. By the end of the 1974 K4 model onward, they were all that way, including the 550.

To bypass a dead switch: you can just plug the Black wire in the headlight into the Brn/White feeding the left Hi/Lo switch, or else to the Brn/Red (some are Brn/Yellow) that feeds the middle fuse in the fuseblock, if you want to keep the same fuse arrangement (if your fuses still work, that is, but that's another topic!). The headlight won't go off then during start, but it will light. You can also add a small relay (like in my Start Button Saver relay kits) to switch the light off during start as follows:
Connect the NC (normally closed) contacts to Black and Brn/Red, then connect the coil to Green and the the Yellow/Red (or Grn/Red if it is the later K4) that goes to the Start Solenoid. This arrangement will pass power to the headlight until the Start button is pressed, and pulls open the relay while starting, to kill the lights.

[Deltarider]

Glad we never had that silly arrangement on European models.

[PeWe]

Glad we never had that silly arrangement on European models.

+7
My CB750K6 is an European bike. Never a problem to start with headlight on. My bike has an off switch for headlight if the battery is tired.
- Rewire to EU standard?
- Right hand handlebar switch with parking, off, on is available on eBay new and used.
My EU K6 has K1 blinkers and rear lamp.
- I had an issue with a jumper that had been lost when I restored the bike to the bare frame.
Jumper between black and brown-white circuit making things to not work when lost since brown-white had no 12V.
Diagram and a multimeter to verify the wiring and measure the voltage when operating the switches.

[HondaMan]

Glad we never had that silly arrangement on European models.

No kidding!
The DOT here has always assumed that only THEY know how to drive, ride, or operate a motor vehicle, and only THEY can come up with ideas on how to make things [somehow] better, and then they pass regulations (which have a force of law behind them in the form of fines) to make it happen...

[rddcw]

Found It !  I must be getting color blind in my old age ?  I had a Brown/Blue Stripe male end wire plugged into a female Brown/Red Stripe .  And a Female Brown/Blue Stripe w/o a mating wire. Also had a Male Brown/Red Stripe wire w/o a mating wire. So process of matching up the "Right" colors to each other.  No more problems and lights work the way they should   

That's the problem changing out the handlebars to Euro Handlebars ordered from David Silvers which required running the handlebar control wires through the drilled handlebars.  Overlooked some of the wire connections in their right color match.

Appreciate all the Help 

[PeWe]

Found It !  I must be getting color blind in my old age ?  I had a Brown/Blue Stripe male end wire plugged into a female Brown/Red Stripe .  And a Female Brown/Blue Stripe w/o a mating wire. Also had a Male Brown/Red Stripe wire w/o a mating wire. So process of matching up the "Right" colors to each other.  No more problems and lights work the way they should   

That's the problem changing out the handlebars to Euro Handlebars ordered from David Silvers which required running the handlebar control wires through the drilled handlebars.  Overlooked some of the wire connections in their right color match.

Appreciate all the Help 

Wiring thru the handlebar is the extra good looking detail to do on a stock bike! My K2 build will get that too.