Headlight, Taillight & Brake light all not working
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Headlight, Taillight & Brake light all not working

This is a discussion on Headlight, Taillight & Brake light all not working within the Technical forums, part of the Caferacer.net Forums category; Good morning, all. I recently did some work on a '80 CB750k. Among other things I cleared the triangle and moved all the electrical into ...

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Thread: Headlight, Taillight & Brake light all not working

  1. #1
    Junior Member brenchao's Avatar
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    Angry Headlight, Taillight & Brake light all not working

    Good morning, all. I recently did some work on a '80 CB750k. Among other things I cleared the triangle and moved all the electrical into a sheet metal box that I made and tacked onto the frame. Since then the headlight, taillight and brake light are not working. I've done some basic troubleshooting, e.g. fuses, obvious breaks in the harness, etc. I was about to start on the switches, but thought I'd reach out to the collective to see if I'm missing something obvious. Thanks.

  2. #2
    Ews
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    Have you tested resistance between power leads and the frame or metal box you made?

    I am assuming it was all working prior to the modifications so that kind of narrows it down to something you changed. You could have shorted something out when moving things around. But my first guess would be that something is grounding out where it shouldn't be
    Dream as if you live forever, Live as if you die today.~ James Dean

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    Senior Member Geeto67's Avatar
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    the obvious would be a fuse, since all lights are on the same circuit and the fuse is the central junction point. did you actually take the fuse out or test it with a continuity tester?

    is your sheetmetal box getting hot when the key is on? it could be you have shorted to the box. Otherwise, get out the continuity tester and the wiring harness and start testing the sections of wire between the headlight, switch, fuse block, etc.....
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
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    Senior Member knappyfeet's Avatar
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    Along with a pocket tester checking continuity, etc.....sometimes I unplug stuff and use leads from the battery to bypass sections of the harness to eliminate obvious items. Assuming everything worked before the modification and now nothing works after the modification leads me to believe you may have a grounding issue or a problem with the switch.

    Good luck and let's see some pics of the modifications.

  6. #5
    Senior Member TrialsRider's Avatar
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    Electrical trouble-shooting usually begins with a wiring diagram, or if you have completely rewired the bike with a wiring diagram of your own making, how close is your bike to this:
    http://manuals.sohc4.net/cb750k/technical_reference/WD750UK.jpg

    Good news is, as wiring schematics go that one is bone simple.

    ... does the horn still work and what else does or does not work?
    Last edited by TrialsRider; 08-09-2019 at 07:25 AM.

  7. #6
    Ews
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    No updates from OP? Are you still having issues?
    Dream as if you live forever, Live as if you die today.~ James Dean

    I feel the need, the need for speed.~ Mavrick (Tom Cruise before he was a big ol' bag of crazy)

  8. #7
    Senior Member XB33BSA's Avatar
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    on any older bike it is pretty much a must do
    this work i tell of
    and that is unplug from each other every terminal conection multi-pin or single
    do it one at a time take your time cand be methodical
    it isd a hateful tediuos job but only needs doing once on each bike
    carefully inspect and clean all ground terminal ends
    if any doubt about condition take key switch apart and clean contacts
    if you have the cylindrical glass fuses you must assure they are still breing held firmly bu the brass deals crimped to wire ends
    a common issue is somebody puts in a 100wat headlight
    or asdds a second 55 job and it will overheat the connection ast each fiuse end and this also anneals thge brass so it looses spring tension clamping effect causding a poor connection with high resistant generating heat and on it goes in a snowballing whirpool of perpetual fail
    examine them clean them and tweak the femal to ensure a tight fit
    better yet use modern fuses
    assemble them with die-lectric viener schlider
    Last edited by XB33BSA; 08-09-2019 at 02:21 PM.

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    Junior Member brenchao's Avatar
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    Four screaming kids in the house took me away from checking this forum, but I'm back. I'm going to check each fuse independently of the fuse box tonight. As far as the sheet metal box heating up - yes, the rectifier got hot as shit and melted my wires into the alternator. I've addressed that problem and moved the rectifier (any ideas for insulating it from surrounding parts?) Never thought to check resistance to the box. Will try that also. The horn still works, and all other electrical appears to be in good working order. Speaking of fuses- when I first started troubleshooting this problem I noticed one of the fuses was burnt out, so I replaced it with the spare. The fuse is "seemingly" functioning as intended, but as Geeto suggests I will test each fuse separately. For argument's sake if the fuse is blown what would be your first line of inquiry? Thanks, all!

  10. #9
    Senior Member XB33BSA's Avatar
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    Quote Originally Posted by brenchao View Post
    Four screaming kids in the house took me away from checking this forum, but I'm back. I'm going to check each fuse independently of the fuse box tonight. As far as the sheet metal box heating up - yes, the rectifier got hot as shit and melted my wires into the alternator. I've addressed that problem and moved the rectifier (any ideas for insulating it from surrounding parts?) Never thought to check resistance to the box. Will try that also. The horn still works, and all other electrical appears to be in good working order. Speaking of fuses- when I first started troubleshooting this problem I noticed one of the fuses was burnt out, so I replaced it with the spare. The fuse is "seemingly" functioning as intended, but as Geeto suggests I will test each fuse separately. For argument's sake if the fuse is blown what would be your first line of inquiry? Thanks, all!
    you really should not have fucked with the electrical system ,pardon my language
    it was already located in the best possible location
    all you have done is tossed a giant red hot monkey wrench into the project
    i know everybody else does it but if you had asked first we could have stopped the madness,prevented pandora's box from being opened
    see,there is absolutely no reason to do what you did
    it only will cause problems,putting everything in a small box is not a smart thing to do..... why not just get it over with and dowse the bike with gasoline and toss a match on to it now

  11. #10
    Junior Member brenchao's Avatar
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    Where's the fucking fun in that? (Pardon my English) If I'd wanted a perfect stock bike I would have bought one. I've heard this piece of advice before and understand it, but when I bought a 40 year old bike to do with as I saw fit I had a good reason, e.g. to make mistakes, and learn from salty veterans such as you appear to write like. I've been off this forum for years, and I know Geeto has a similar view as yours, and you're both not wrong...we just have a difference of opinion.

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