Topic: headlight question

[hymodyne]

hello,

Its been a while, but I have a problem with my headlight, namely it won't work. when I supply power from an outside source, it lights up fine, but when it is plugged into its socket, it doesn't work. I've traced the green, white and blue wires back to their starting points at the handlebar pod and wiring harness respectively. Idiot lights (except for the hi beam), turn signal and brake lights work, just no hi or lo beam from the switch. I'm going to check if the green wire is supplying power from the wiring harness and also look into a new handlebar pod but I wanted to check with some of you here first.

hym

[Gordon]

1st question:  What bike?

2nd question:  If your bike has a separate fuse for the headlight, have you checked and/or replaced it?

The green wire is ground, so should not be supplying any power. 

[HondanutRider]

At the headlight, the green wire should be connected to ground (your frame and the battery's negative terminal). You can see if that wire is the problem by connecting that socket at the lamp directly to some part of the frame.  

The blue wire is for the high beam and the white is for low.  The switch/dimmer alternately connects power from the battery positive lead (through the ignition and fuse) to these wires.  The switch will have another wire connected to it supplying this power from the battery positive terminal - that connecting wire is usually black.  If you measure its voltage it should register your battery's 12 volts with the ignition turned on, against the frame ground again - if not then its circuit is faulty (i.e. the black wire from the switch back to the ignition, which connects it to the fuse and the positive terminal...BTW is your fuse OK?).  If there is power at the switch measured at the black wire, then for test, directly connecting it to either the blue or white lead that runs to the light should fire your headlight  (i.e. by-passing the switch).  If it doesn't then you have a problem with those white or blue wires (I doubt it), and if it does fire the bulb then your switch or its connections are likely bad.

Isn't tracing electrical gremlins fun?

[hymodyne]

thanks for the replies.

Its a cb500 K1 frame with a '76 550 engine.

It has just one fuse which is OK. I'm thinking its the switch since the problem just began a few days ago. I'll do some more hunting around though, as I've found at least two wires that were frayed or about to break inside their insulation while I have been looking for the problem. When I opened the handlebar pod, I really didn't see any difference in the headlight slide/switch movement and parts. Is it possible that the contacts on this switch have worn out; perhaps that is why honda changed to a toggle hi/lo on later model cb's?

hym

[Gordon]

Worn switch contacts is definitely a possibility.  I've had to deal with that on a few of my bikes.  Cleaning them up with some very fine sandpaper has worked well for some, but for others it's only a temporary fix because the non-corrosive plating on the contacts has worn through, and it doesn't take long for the metal under the plating to start causing problems again.

[madmtnmotors]

The hi/lo switch on my 78' CB750K wore slap out. I could jiggle the toggle side to side and get momentary contact which led me to the culprit. $1.99 3-position micro toggle switch from Radio Shack works like a champ. Soldered the original wires to the new switch, now I even have an "off" position. I'll post some picts tommorrow, actually works very well and doesn't look too hawky. Even fit within the stock housing once the original switch was removed.

[Spanner 1]

If the green wire from the h/l plug is not grounded = no hi or low beam, or if the brown wire-with-red-tracer that goes up the handlebar to the h/l switch does not have power = no h/l...... look there.


Just an aside..... Green wires on our bikes are always Ground/ frame; Black, Brown and Red carry battery + voltage.
Ign. switch 'Off'.... RED wire is + always, Ign. 'On'... sends + to Black and Brown.

[hymodyne]

Many thanks for the replies and suggestions. Hopefully I'll get this worked out soon so the night rides can resume...

Hym

[333]

Look at the ignition switch.  Contacts go bad there as well.