Need help from electrical gurus w/intermittent short blowing ignition fuse

Discussion in 'The Garage' started by niided, Dec 31, 2012.

  1. niided

    niided Been here awhile

    Dec 18, 2005
    I have been able to complete many diy projects and solve/repair a bunch problems on my m/c's and cars by searching

    Google. I also have this posted on Ninja 250 org. forum. Most of my time is spent on the Adv forum.

    But this one electrical problem w/my Ninja 250 has me totally stumped . I have read extensively about the problems that

    could be cause of the #3 10a igniton fuse blowing. My son's 2004 Ninja 250 has an intermittent short that is causing #3

    ignition fuse to blow. The first time it happened while on the hwy, lost power and had to be towed home. #3 fuse was blown.

    Here is what has transpired so far;

    1. Replaced fuse and turned on ignition, immediate pop.

    2. Removed gas tank to look for obvious breaks in harness and connections, nothing found.

    3. put new fuse in, good to go. Started up bike, tried pulling and twisting wires at obvious connections relating to #3 fuse, all

    the safety switches, ignition, etc. Could not recreate the short.

    4. Put the tank back on, tried starting, as soon as I turned the key, the fuse immediately popped.

    5. Took the tank off was going to do ohms check on connections, but short went away.

    6. Tried running the bike for about 30 minutes while on a stand, revving up rpms, thinking it might be heat related. Bike

    kept running.

    7. Buttoned the bike back up. Took it for a spin, 10 miles from my house, blew the fuse, towed back home.

    8. With the #3 fuse blown, was going to track the short by w/multimeter, had to take the tank off to get to the connections,

    short disappears again.

    9. I now have the harness pretty much apart and checking individual wires for any sort of fraying or pin holes. Have found


    10. I took apart both bar end housings to check the kill switch and clutch switch wiring. Took the bottom cap off the ignition to

    check wiring. Checked the wiring at kick stand switch and neutral light switch at engine. Everything looks good.

    My friend thinks it might be coil related and t when it heats up while riding it might cause a short. I have blown the fuse while

    the bike was cold after placing the tank back on, so I don't know about his theory. I pulled apart the junction box and all the

    pins and solder points look good. Looking at the schematics , could a bad rectifier or ignition module cause a short to the

    #3 fuse? How about the coil? By the description I provided, it seems to be that it is most likely a wire to ground causing a

    major short. I have closely inspected the wires under the tank for even a small pinhole but nada. All the plastic connectors

    are intact. I have traced the wires forward to dash and handle bars. The only thing I haven't traced are the wires running

    from the junction box rearward as they are not connected to ignition fuse. Any ideas would be welcome. I am about to throw

    in the towel and maybe buy complete new harness, but that might not even be my problem.

    The big problem is that the bike is running fine right now so I can't use the meter to isolate the culprit.

    Thanks for your time,

    D.T. Niide
  2. ScEd

    ScEd Been here awhile

    Feb 16, 2004
    UpState SC
    Usually a wire shorting to ground will reveal it's-self soon. Sounds like you have checked the harness thorough enough to begin looking at components such as the rectifier. You could try isolating the components one at a time with a new feed wire from the battery fused separately. This would at least allow you to eliminate the possibilities.
  3. vtduc

    vtduc Been here awhile

    Dec 25, 2006
    From your description, I would suggest the wire harness may be rubbing and grounding on the underside of the gas tank.
  4. mark1150

    mark1150 Been here awhile

    Oct 10, 2010
    Wisbechistan UK
    It does sound like the gas tank has a part in this i.e. shorting.
    I'd be inclined to insulate the tank by means of plastic builders bags and tape, if only to isolate the area.
    If it runs fine while insulated you can be almost sure that the problem lies in the loom beneath the tank.
    Let us know how you get on.
  5. concours

    concours WFO for 44 years

    Dec 2, 2008
    Kensington, NH USA
  6. Guy Young

    Guy Young Long timer

    Jul 8, 2006
    North Chesterfield, VA
    Personally, I would make up a test light to replace the fuse so you don’t keep blowing them. A “smoke test” is certainly one way to do it, but you risk further damage to the wiring harness.

    Pick up a “power on” test light from one of the auto parts places, similar to this:


    Get a couple of male .250 spade connectors and crimp on some leads that are several inches long.
    Pull the #3 fuse and plug the spade connectors into the j-boxes’ fuse clips. Narrow the width of the spades (if necessary) so they will fit into the fuse clips.

    Alternate to the above "packaged" test light if you have a soldering iron/gun and minimal soldering skills, would be to get a single filament 12v automotive bulb, and solder the leads from the spade connectors directly to the bulb.

    Connect the spade’s leads across test light and turn on the ignition. Due to normal circuit loading (without a short circuit), the bulb may glow dimly.

    Begin to manipulate the harness (yank, tug, pull, etc.) at various locations and look for the test lamp to go bright. This will indicate that the short has reappeared.

    That brown/black wire out of the j-box only goes to so many places (igniter, kill switch on the RH handlebar switch cluster, instrument cluster), so concentrate your harness manipulation in those areas. Obviously, temporarily install the tank (with the ignition on and monitoring the light) and jostle it back and forth looking for a change in lamp brilliance.

    FWIW - power comes out of the kill switch as a red wire. It goes to the start pushbutton in the same cluster, and to the coils. If the switch is in the "run" position, that "short" would transfer through it back to the fuse. The coils are under the tank, so I would look very closely at those leads and their routing.

    That’s the best I can offer. Good luck with it.

  7. tommu56

    tommu56 Long timer

    Sep 11, 2011
    limerick pa / waterville pa
    If you have the wiring diagram for the bike put little larger fuse (12 amp) in and refuse each section separately with a fuse that will narrow down what section it is in.

    I call these shorts a swinger because its ok until the wire moves with the wind or vibration.

  8. dtysdalx2

    dtysdalx2 PITA but useful

    Aug 1, 2004
    Moneyapolis, MN
    Sounds like you may blow something, but then at least you will find the problem.

    I say get a schematic and trace all the wires in the #3 circuit. You just have to keep at it.
  9. tubebender

    tubebender Shakin' all over

    Feb 8, 2007
    I'm not going to be much help, but my sons former 250 Ninja had this problem. I had to go get him more than once.

    Drove us nuts trying to find the short. It was a rub through on the main harness. I'll ask him tonight if he remembers where.
  10. niided

    niided Been here awhile

    Dec 18, 2005
    Thanks for all the replies. It sure helps to get some different ideas.

    Believe me, I was at a point where I would have put in a jumper wire to do the "smoke test" but bike is in a perfect running

    state now and not shorting out fuse. Right now I have it apart and going through the individual wires associated w/the ignition

    circuit. Like suggested, I suspect something under the tank and up around the neck towards handle bars. Hopefully I will be

    able to find the wire that is shorting out. If not. I will put things back together and try to recreate short.

    Good suggestion on the test light. I will set mine up as instructed as I have gone through a number of fuses.

    Also good suggestion on wiring/fusing suspect components on a direct separate line to battery. I will keep that in mind

    while trouble shooting suspect components.

    I will keep the board informed of my progress, or lack of. Might be hard getting any trouble shooting done today w/all the

    Bowl games being played.

  11. ttpete

    ttpete Rectum Non Bustibus

    May 13, 2009
    Dearborn, MI
    Look anywhere there's a chafe point, especially where the harness runs over a square or sharp edge. Sounds like the tank is pressing the harness against something and has worn through the insulation.
  12. tubebender

    tubebender Shakin' all over

    Feb 8, 2007
    OK, asked my son and he remembers we found the short where the harness is routed through a hook on the main frame tube under the gas tank/seat junction. There was some weld spatter there and it rubbed through.

    Hope this helps.
  13. Warin

    Warin Retired

    Aug 30, 2012
    Do configure a "Light Globe " fuse (as per above) ... use an old headlamp globe ... parallel hi and low beams... this should give you enough power to run the bike .. the globe might glow a pale yellow/orange but won't fully light up. When the short happens - it will light up. Another idea is to use a horn instead of the light globe ... but I don't like the sudden sound!

    Take a look at the bottom of the fuel tank itself ... look for where the paint has been rubbed .. this could indicate where the wiring has been contacting the tank .. and where the wires are shorting.

    The other place to check are the wires where they flex with the handle bar being turned ...

    With time you will find it.
  14. niided

    niided Been here awhile

    Dec 18, 2005
    Thanks all for the inputs.

    "OK, asked my son and he remembers we found the short where the harness is routed through a hook on the main frame tube under the gas tank/seat junction. There was some weld spatter there and it rubbed through."

    Thanks for checking .

    "Take a look at the bottom of the fuel tank itself ... look for where the paint has been rubbed .. this could indicate where the wiring has been contacting the tank .. and where the wires are shorting.

    The other place to check are the wires where they flex with the handle bar being turned ... "

    I will give this shot, looking under tank for any wear marks and trying to match up w/wires.

    After close inspection of wires mostly associated w/ignition circuit, I couldn't find any suspect wire. There are several wires

    that are spliced together (where two or three wires are crimped to one main wire and branches off to other circuits and just

    taped over) . I rewrapped these spliced spots.

    I hooked up the bare harness again without wrapping the wires hoping I could recreate the short and spot the shorted


    Put the #3 10a ignition fuse in turned bike on, fuse stayed intact.

    Started the bike, bike ran, fuse still intact. Pulled and twisted on wires at all connections/plugs, bike still runs.

    Put the tank on, bike still runs. Put pressure on tank, moved tank from side to side, bike still running.

    Turned handle bars lock to lock several times, played w/all switches several times, bike still runs.

    Next plan is to throw m/c ramp in back of buddy's pick-up, have him follow me while I ride, try to recreate short like it

    happened the last two times. If fuse blows, hopefully it does, we will try to isolate and track suspect wire with meter right

    there and then.

    I will post with any success or failure. I am also thinking of investing in a new harness from Bike Bandit.

  15. PeterW

    PeterW Long timer

    Nov 11, 2005
    Gold Coast
    Use your nose, the burnt insulation has a distinctive smell.

    And yes, wiring rubbing on frame is the most likely.

  16. aussie_king_mick

    aussie_king_mick Been here awhile

    Jul 4, 2008
    Sydney, Australia
  17. Midnightventure

    Midnightventure -

    Dec 23, 2008
    I like that.
  18. NoTraffic

    NoTraffic n00b

    Dec 25, 2012
    I just had a similar issue with a Suzuki SV650. I had a short somewhere that kept blowing a 15A signal fuse. Like you, I had gone through about 10 replacement fuses and reproducing different scenarios that would keep me frustrated (blew when put just to "on", blows after 10 minutes, blows after I hit brakes, etc).

    After resolving it just yesterday, here is what I would do differently (take about 2-3 days to do this):

    1) Remove all fairings, seats, passenger seats - anything that could possibly have a wire behind it.

    2) Trace the wires that are leading to the blown fuse. Take off all loom, electrical tape, and start inspecting it. When you go through one section, call that "Done". (I found some suspect wiring which contained pools of water, so just untaping it does you some good).

    3) Look at nearby fuse placements that may be coupled or linked to that starter fuse as well. Trace those wires. If you traced all the visible wires, consider yourself halfway done. It is NOW a wire that you cannot see which is shorting/grounding and is usually touching a ground. Trace all metal components and look for a hard to reach wire. This is usually the cause of the short.

    This is what I did with my SV and finally found a hard to reach harness under the tail section that was completely out of sight and one which I would have never guessed to cause a short. It's only when I started to trace every fathomable piece of electrical wiring that I found this to the culprit.

    Good luck, just takes some patience and persistence. I almost threw in the towel too.
  19. Grinnin

    Grinnin Forever N00b

    Dec 10, 2005
    Rectifier -- not all that likely; Ignition module -- more likely.

    The one diagram that I looked at showed the wire from that fuse going directly to the ignition unit. Wires branch from there to several locations (tachometer, coils, ground, diodes and onward to safety switches).

    There's the ugly possibility that there's a short inside the ignition unit itself. Probably too pricey to buy on pure speculation and hard to find someone who will lend you theirs.

    When working with a dodgy ignition on an older bike, I made a bunch of short wire jumpers. Each jumper was a 2" wire with a male spade on one end and female on the other. If you did the same with several inline fuse holders with 5A fuses in each, you could identify where the current is going.