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    Default Blowing Ignition Fuse

    I rewired my bike after blowing a fuse using the turn signals. The bike had one other electrical problem the neutral light would stay on dimly when in gear. I used a multimeter to test the switches and looked inside to check the soldering. Rewired it up and it tested fine parked with the engine and headlight running.

    After the rewiring I tested the turn signals parked and running, they worked but I blew the 20 amps fuse from the bat to ignition trying to kick the bike to life. Using the horn makes the tach needle jump and makes the turn signal indicators, oil light and neutral light, spark very dimly along with the frequency of the horn. When the bike is running and the horn is removed from the circuit the same lights flicker along with cadence of the engine. Iím running two 12 gauge wires for main hot and ground and another set of 16 for the lights hot. All the items up front use the same ground.
    Iím running points with a 5 ohm coil. All of the lights are low amp leds. Bike is kick only and the battery is rated 8AH.

    Should certain items on the bike have their own hot and ground?

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    Quote Originally Posted by AbbandonZK View Post
    Should certain items on the bike have their own hot and ground?
    Some do some don't.......

    What kind of bike do you have??????? What wiring diagram are you going by??????????

    It sounds like you have a grounded hot and a very weak ground........

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    Quote Originally Posted by Tattooo View Post
    Some do some don't.......

    What kind of bike do you have??????? What wiring diagram are you going by??????????

    It sounds like you have a grounded hot and a very weak ground........
    Well, every electrical part does have a hot and a ground, that's kinda how electricity works.

    I agree with Tattooo that at the least you have a weak ground.

    And I will say there is no place on a bike where 12ga. wire is necessary. The loads are not that big, and more importantly, the runs are short. 14ga. coming off a 30A breaker is as big a wire as needed, with 16ga. down to 20ga. is sufficient for most of the circuits.

    On older bikes the ground is often through the frame on many circuits so frame connections need to be clean. Powder coat is hell on grounds, but paint or rust don't help conductivity either. Newer bikes have dedicated ground wires for most circuits as that is more reliable, especially for lights.

    Looks like you have more work to do. A multimeter is a big help diagnosing problems. Without more specific questions and details, it's hard to help you.

    Jim

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    Quote Originally Posted by JBinNC View Post
    Well, every electrical part does have a hot and a ground, that's kinda how electricity works.

    Correct but kinda, What about a neutral switch........ It doesn't have a ground it is the ground.......

    I just answered his question the way he asked it.........

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    Quote Originally Posted by Tattooo View Post
    Correct but kinda, What about a neutral switch........ It doesn't have a ground it is the ground.......

    I just answered his question the way he asked it.........
    A neutral switch does have a positive and a ground. It's job as a switch is to ground its positive to compete a circuit and turn a lamp on.

    Jim

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    Its a kick only shovelhead. Im using the 82-95 switches and everything on the switches is connected except for the starter black wire.

    Alternator>30 A Circuit Breaker> Battery POS> 20amp blade fuse> Igntion swtich B

    Ignition Switch IGN> 12 Gauge Main Hot connects to nuetral light, oil light, Tach power and horn switch

    Igniton Switch IGN> run stop switch to 5 ohm coil to points //this is its own line of wire

    Igniton Switch IGN> EP34 turnsignal relay> turn signal switch> front and rear turn signals> turn single dash indicator //this is its own line of wire


    Igniton swtich L connected to headlight swtich selector, tach back light, speedo backlight, runnning lights, license plate light.

    All the component grounds are ran back to the battery along the main ground cable and the frame has a ground cable also going back to the battery from the fender mount. Nuetral and oil lights are grounded where the need to be.

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    If the handlebar switches are aftermarket, I have found that the insulation on the wires is of very low quality plastic, and if you pinch one at the switch or somewhere along the bars, you will get a short even though the insulation appears to be whole. Easy to pinch in the switch housing because not much room and the brake or clutch perch are also clamped over the wires. Just a thought.

    Jim

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    Quote Originally Posted by JBinNC View Post
    A neutral switch does have a positive and a ground. It's job as a switch is to ground its positive to compete a circuit and turn a lamp on.

    Jim
    So a NEUTRAL SAFETY SWITCH 1959-1998 OEM# 33900-59 has two wires????? Nope....

    Like I said I answered his question the way he asked it.......... That's the way I read this....... {Should certain items on the bike have their own hot and ground?} If you read it differently that's fine with me....

    Believe me I know how electricity works.........

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    Quote Originally Posted by Tattooo View Post
    So a NEUTRAL SAFETY SWITCH 1959-1998 OEM# 33900-59 has two wires????? Nope....

    Like I said I answered his question the way he asked it.......... That's the way I read this....... {Should certain items on the bike have their own hot and ground?} If you read it differently that's fine with me....

    Believe me I know how electricity works.........
    Neutral switch ground is the transmission top or case. The wire terminal is the positive and the body of the switch is the ground. Yes, it does not have a dedicated ground WIRE. It might be just semantics causing the misunderstanding, but a switch is a switch. (And some neutral switches do have two terminals.)

    Jim

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    I'd disconnect all but the ignition then ops check by starting then performing a charging system test with a meter. If it runs fine and tests good, connect one lighting subsystem and investigate. If good, add the second.

    That way you troubleshoot ignition and both lighting systems in sequence. I put accessories on a separate breaker or breakers after the switch because accessory failure should not interfere with the engine. A blade breaker is easy to remove for troubleshooting and fits inline blade fuse holders. (Glass fuses have no place on motorcycles and were used because they were cheap. HD used breakers because they were smart.)

    Wiring should intentionally facilitate easy troubleshooting like stock Shovel wiring did.
    Last edited by farmall; 02-21-2020 at 10:13 AM.

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    I tend to depower and use the ohmmeter on the circuit, then isolate the component.. If the problem goes away? It is the component. If it does not? It is the wire..

    Also, it is nice to just sort of poke and shove wires a little bit when you do this. A lot of times you will find a chafe that is an intermittent problem. Those can be very hard to diagnose.

    You can test your grounds the same way.. One lead on the - terminal of the battery, and then check the resistance to ground. If you have a high resistance, you have paint or rust or a bad crimp or something you need to address.

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    Quote Originally Posted by JBinNC View Post
    (And some neutral switches do have two terminals.)

    Jim


    Yep but NOT his..............

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    With the ignition off and the black multi lead on the negative post and the red on the metal surfaces of the bike I have .5 ohms of resistance.

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    Quote Originally Posted by AbbandonZK View Post
    With the ignition off and the black multi lead on the negative post and the red on the metal surfaces of the bike I have .5 ohms of resistance.
    Ideally it would be zero for such a short run, but that's really not a lot.

    Do you have continuity to ground through your ignition wire when you unhook it?

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    maybe something in here might help ya:
    Tutorial: Motorcycle Wiring 101
    https://www.bikeexif.com/motorcycle-wiring

    and got this diagram:
    Click image for larger version. 

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    When I disconnect the ground wires from the battery and run the black lead to frame ground. The ign post on the switch beeps for continuity the lights show a voltage drop of 1.9 no beep. When the main ground is tested the L position beeps for continuity and the ign post shows a voltage drop of 1.5.

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    Continuity between the ignition lead and ground is a problem..

    I would disconnect that and trace down it.. Because a low impedance connection between that lead and ground is what is blowing your fuse.

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    Quote Originally Posted by AbbandonZK View Post
    When I disconnect the ground wires from the battery and run the black lead to frame ground. The ign post on the switch beeps for continuity the lights show a voltage drop of 1.9 no beep. When the main ground is tested the L position beeps for continuity and the ign post shows a voltage drop of 1.5.
    Yep just like I said in my first post...............

    Quote Originally Posted by Tattooo View Post
    It sounds like you have a grounded hot and a very weak ground........

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    Quote Originally Posted by confab View Post
    Continuity between the ignition lead and ground is a problem..

    I would disconnect that and trace down it.. Because a low impedance connection between that lead and ground is what is blowing your fuse.
    Is the key switch old? They are disposable and I get about ten years use out of Drag Specialties generics. They've been known to short to ground internally.

    I ohm across the disconnected switch in all positions and ohm each terminal to ground in all positions. (If it's the least bit loose I replace it. They're cheap.)

    You can bypass the key switch using a jumper lead (disconnect the switch) to check each system without switch involvement.

    BTW ensure the points are open when checking the circuit because they apply ground to build up power in the coil. I would disconnect everything else and ensure the ignition works by starting the engine as that's the easy way and a short to ground will prevent start.

    When a test light connected from the points side of the coil to ground lights, the points are open (that's how static timing lights work).
    Last edited by farmall; 02-21-2020 at 6:33 PM.

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    Thanks for the help guys it was the tachometer that was passing voltage. The light circuit read to the multimeter as a open circuit. And the hot to ground had a voltage drop of 1.9. Once I clipped it off the bike I had two separate circuits. I also discovered the headlight outer housing passing voltage thru the frame. The headlight has a blue high beam indicator light that’s unshielded.
    Last edited by AbbandonZK; 02-21-2020 at 7:29 PM.

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