Topic: Okay . . . Fuses located on '80 CB900 custom & HEADLIGHTS FINALLY WORK !

[Treeguy]

I feel sorta' retarded for not checking the steering cover  , but secondary fuses found and the headlight circuit fuse not blown. All other accessory lights come on appropriately, with the exception of the hi-beam indicator, and the headlight itself. I checked the headlight itself by attaching it directly to the battery and it lights up fine. I am open to any suggestions about a methodical approach to troubleshooting this problem. The bike runs, the horn is missing . . . I found a wiring diagram online, but was having issues printing it. Any input would be appreciated . . . I have a cheapo multi-tester, and a 12V test probe. Not sure I fully understand the headlight circuit . . .

[w1sa]

I,m not an expert on these electrics, even though Ive got an 81 cb900 myself.
The first thing I'd do is verify the connector/pins to the headlight bulb are sound and connected. If so, use your meter to see if power is getting to the connector. Checked the bulb filaments? If so check the ground wire going away from the bulb for security etc.

Is the taillight working at the same time you switch on headlight?

Geof

[Treeguy]

I believe i checked for power at the connector, but i am not to sure of my electrical testing ability yet. Yes the brake light comes on and stays on when the head light is switched from hi-beam to lo-beam. Where is the ground for the headlight circuit? I saw a ground by the coils, and another one directly to the headlight case, and the other one off the battery attached to the frame. 

[troppo]

G`day treeguy
you have a multimeter, thats a good start, find a good earth and check the headlight power line at the headlight for power, then go back to the next join in that wire. Make sure power is going to and coming from your headlight switch when its turned on (i am presuming it is because you said your tail light is light up. if you have power then you probably have an earth problem, find a good earth point, put the other probe to the earth wire for the headlight and you should get a reading to show that theres continuity (try a good earth point and the battery negative to see what that reads)
hope this helps mate
cheers
troppo

[w1sa]

Treeguy,
Some more info that might assist.

Power to the HL comes from the Ignition/Key switch (obvious) via the Fuse box to the StarterButton/Switch housing (the HL/ParkingLight location).
According to Clymer's manual:
The wire from the HL switch to the Hb/LB/Dimmer switch is Blue/White (LW). Then one Blue and one White to HL and a parallel Blue wire feed to the HB indicator light.

Most Instrument/front traffic lights (incl. the HL) each share a common frame ground via a common dark green wiring (Dg) (Might not be so dark after 28 years)
This also applies to the stop and tail/license plate (Dg), amongst others.
According to Clymer's the front frame ground is hard wired to the stop and tail lighting grounds.
This might indicate that should you lose a frame ground at one end you will still have ground via the other (could be wrong!)

If you check all appropriate connections for power/ground security and the bulbs appear serviceable (always pays to have a spare bulb that you know is good) then, it might be the switching. Especially as you say the HB indicator also fails to illuminate (it's wired in parallel).

I've previously had trouble with the 'slider' type switch on this bike that controls/actuates the blinkers/indicators. It was physically worn down internally and could not make good connection. I had to replace the switch housing.
Both of the HL swithes might be mechanically similar to the indicator switch. I can't recall, but they do operate the same.

So if you've tried everything previously mentioned, including opening the switch housing and checking the internals, you might as well continue and check the switches and specific wires for continuity as well.

 Identify the wiring colours previously mentioned. Use your meter to confirm continuity between the switches/connectors (via appropriate colour trace) and also across the switches via wire terminal points each side. If all checks out ok so far, you should be able to get good continuity from one side of the circuit to the other with the switches 'on'
(physically, not electrically). In this case, connect meter from battery/ign sw side of HL switch to alternate Blue or White wire termination points(also testing the HB/LB switching) at the HL connector. If you get good continuity your problem is most most likely outside that parameter. i.e. thru the HL bulb to ground or back across the circuit before the HL switch. If so check continuity between Red/Black in HL switch and Red/Black in the Fuse panel.

That should establish whether your circuit switches/wiring between the HL fuse point and the HL/HB Indicator grounds is OK.

If that all checks out OK, power to the fuse point, fuseholder connections etc, even changing the fuse for a known good one, could  be considered.

Hope you shed more light than I can.................Geof
 

[Treeguy]

Okay,
       I now have continuity in the left hand control switch, but I still have headlights that don't work. I am not sure where to proceed next. I am having trouble locating the headlight circuit in the wiring diagram. Since I am not getting power to the hi-beam indicator (I was told it's wired in parallel) it seems logical that the short is before that circuit all together  . . .   I am open to any suggestions !  If any one can vaguely point out the headlight circuit starting from the battery, that would be helpful too! I have appreciated all input! Enjoy whats left of the weekend!  Shane
 

[Treeguy]

Hmmm . . . this evening I unplugged the dimmer switch connector and tested between the G wire (ground) and B/W wire (power) and found 12v (this was on connector that comes from the main wire harness). So, I appear to be getting power up to the connector, but once I reconnect I get no light still. I redid my continuity tests on the dimmer switch (horn, turn signal, etc) and passed with flying colors and Ig. switch was also tested and is fine. So i rough connected between b/w & b/w with gator clips, and attached a couple gator clips to G (switch side)  and the other set to G (ign side) and put my multimeter in series between G & G and turned the key to on, and nothing . . . it seems I have a problem with the ground, but I am uncertain. This is my first experience doing my own electrical troubleshooting . . . if anyone spots an error in my logic or method let me know . . .

[w1sa]

Treeguy,
If you verified power to the connector, and the connector pin/socket is ok, you should be able to rejoin the connector and verify power onwards to the H/L switch.
But to be sure of good connection, with connector unplugged, bridge the blue /white wire connection (For this, connect your test light or meter ground to the same ground pin you used to get power at the connector (on ign side). Once you verify power to the H/L switch, then step across the H/L switch. If you have power across the H/L switch, you should be able to get power at the HL bulb (either/or Blue Or White wire.)
 Try this sequentially using the same ground pin you used to get power at the connector.

Be careful to use the Green ground applicable to the HL in the connector, as Clymer's indicates two green wires thru that connector. Diagram shows green ground wire you need is central in the connector?
If you fail to get power at any point, it would indicate a open circuit, possibly caused by broken wire (not most likely, but not impossible)

 If you get power at each point out to the HL bulb, your assumption of a ground problem would seem correct.

Assuming you verify power to the power side of the bulb, connect a bridging wire from the HL ground terminal/wire at the H/L to the same ground pin in the connector (ignition side)you used to verify power up to the bulb. 
Does the HL work, when switched on?
If so, the ground problem is between the HL and the connector (which could be bad wire or pin connection between the HL side and the ign side.) Verify this by rechecking from the HL  ground terminal point to a frame ground. If the HL also works with this ground, but still refuses to work with the Connector plugged in, the fault is almost certainly the connector/pins or ground wiring back to the HL.

Good Luck.................................................Geof

[Treeguy]

Geof,
 First, I thank you for your time and input. I have more questions than answers. Today I took apart the dimmer switch and tested the G wire for continuity, frustratingly enough it passed, I tested (still the G wire) from the switch side down to the connector (the longest wire portion) then tested to the clutch switch G wire, then tested G wire between headlight connector and switch connector, again got continuity in all of them. If you recall I earlier reported finding 12v between the B/W socket and G socket on the connector (ignition side). Logically I assumed that since there was power there I could connect my 12v test light across those sockets (bypassing headlight switch altogether) and get light . . . but I got nothing . . . So i pressed on . . . and using that same B?W socket i connected straight to the negative post on the battery and I still got no light (not sure what that means). Why I am getting 12v across their and not getting light is confusing. So I then focused my attention to the ignition switch. I unplugged the ignition switch and set it aside and focused my attention to the plastic connector, I connected my 12v test lead between BAT₁ & IG (R & Bk wires) and the sucker lit up! Woo hoo !! I separately tested TL₁ and TL₂ (BR/W & Br wires) and no voltage (assuming this is normal since this circuit is for turn signals & brake light?)   I also connected between PA & BAT₁ (Br & R wires) and also got 12v. To simulate the ign. switch in the on position, I connected BAT₁ & IG, and at the same time also connected TL₁ & TL₂. And I finally got voltage across TL 1 & 2, and further tested it by switching the turn signals. So i definitely know that I am getting power to the ignition switch, but I am not sure how the power is distrubuted to the headlight circuit from there. To recap . . . the bike runs fine, it starts, but no headlight. I have tested both left & right controls for continuity, and they all passed. I am a little confused  . . . will sleep on it again! Again, I am a newbie so if anyone spots any errors in my method or logic please let me know.  Shane

P.S. Geoff I will try the step method of tracing power to & across the switch but not sure I will get any meaningful results. I am not as confidant that I am getting the power that I assumed I was getting at that connector any more since my 12v test light didn't light up across the wire G or neg. battery terminal (ign. side). Thanks again for your time to write that response . . .

[Treeguy]

Ok, I tore apart the starter button on rt side control, and after cleaning the starter button contact plates I got the headlight to work !! Thanks for all the input! Now just waiting for the new tires . . . Wooooh  Hoooooo   !!!!  Now I can start belly aching about something else on here !!