Electrical troubleshooting
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Thread: Electrical troubleshooting

  1. #1
    Senior Member 80cb400t's Avatar
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    Electrical troubleshooting

    I finally got my cb160 running, and neither the headlight or tail lights work. The bike is charging (whew) and the parts bike even has an H4 connector so I may attempt to go LED (I assume I should figure out how to add a regulator or upgrade to a combined one)
    I don't really know what I'm doing with electrical troubleshooting so go easy and simple on me and if there are any recommended resources on testing I would appreciate those. I understand the general concepts but not how to go from those to practical problem solving.

    What I've checked
    Headlight: If I connect the blue to + and green to - = light
    if I connect red to +, still green to - = no light
    Bike running = no light, no matter the switch position or key position (should come on always with third key position (assuming off = 1, on = 2, on with lights = 3)).
    Key to third position = light behind the speedo comes on

    I think this tells me one of my filaments is burnt out and that I need to retrofit my sealed beam. I'm not sure if my wiring to the headlight is working as it should.

    Tail light:
    When bulb is connected to ground and positive = light,
    When bulb is installed, both running and not running: no light
    I tried connecting white wire to + and blue to - (which told me nothing I think because that's not how the light works),
    Then tried connecting the ground that's soldered onto the tail light to battery - and one of the wires at a time to battery + and got no light
    I think this tells me I have a problem somewhere in the tail light holder contacts?
    Last edited by 80cb400t; 08-18-2019 at 07:09 PM.
    1980 CB400T - 1 running, 1 parts bike
    1965 CB160 - 1 kind of running, 1 parts bike

  2. #2
    Senior Member mike in idaho's Avatar
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    The ignition switch has four positions, off, on, on with lights and park light. In the lights on position the main switch feeds 12 volts to the brown wire going into the dimmer switch. Blue and red are high and low beam, coming out of the dimmer switch. Tail light receives power via the white wire from the main switch blue wire is brake light. The early Hondas didn't have a dedicated ground wire in the main harness, that makes troubleshooting a bit more difficult at times.
    80cb400t likes this.
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  3. #3
    Senior Member 80cb400t's Avatar
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    That really helps, your description reminded me that I need to look at the wires into the switches on the wiring diagram and consider the options.
    I think I've got a bit better of an idea after more reading and youtube videos, if I understand correctly I want to make sure I have voltage from the battery all the way to the headlight with the circuit active. I'm guessing I'll find that either the brown wire is not sending power or the power isn't making it through the switch on the bars.

    I'm not 100% sure on testing the ground, is it as simple as setting to resistance and putting one post on the negative terminal, one on the case of whatever you want to check is grounded?
    Last edited by 80cb400t; 08-19-2019 at 02:34 PM.
    1980 CB400T - 1 running, 1 parts bike
    1965 CB160 - 1 kind of running, 1 parts bike

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  5. #4
    Senior Member 80cb400t's Avatar
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    I think I'm getting it, I fixed the tail light just now using the multimeter to point me to the fairly standard issue: corroded bulb to holder contacts
    So I checked for voltage with key to third (lights on) position, got it all the way to the final connectors. I then checked continuity from the bulb holder bullet connectors to the 1157 contacts. Hmmm I can't get it where the bulb touches the contacts. A little brass dremel brushing and we're all good.

    Now to the headlight, baby steps here
    1980 CB400T - 1 running, 1 parts bike
    1965 CB160 - 1 kind of running, 1 parts bike

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