great ride, fuse blows - Help!

Orsonoce · Jul 8, 2012

Hi folks, spent the last few months getting my babe in shape for the summer season.
Changed the whole wiring harness and headlamp harness.
Given I am no electrics expert I was quite surprised to see my lights and horn work properly (ignition on, engine off).

Today went for the first ride after months (will post pics later this week!). all good. bike running smoothly. actually, running supergreat!.
Then, after 20 miles or so I decide to turn my lights on (switching ignition key to 'light' position with light switch on headlamp 'off') -> immediately fuse blows, bike stops.
Put a new fuse in (light off this time!) and ride back home with no probs.

Can someone tell me how I check what I need to fix? Please do consider I know zero nothing about electrics, but I own a multimeter (but not sure how to use it...), so be patient with me, and ideally give me explanations like you're talking to your wife... (eheheh)

L.A.B. · Jul 8, 2012

Orsonoce said:
Then, after 20 miles or so I decide to turn my lights on (switching ignition key to 'light' position with light switch on headlamp 'off') -> immediately fuse blows, bike stops.

From your description, it seems like there's a short in the brown/green [NG] wiring somewhere.

If you study your wiring diagram, then you should see that the NG wiring goes from Ign. Sw. terminal 3 to the tail lamp and also to the pilot lamp and instruments.

I suggest you check the obvious things first, like a loose wiring connector or chafed wiring that could be casing the short. Also check the tail lamp assembly and bulb holder very carefully.

Orsonoce · Jul 8, 2012

thanks Les, is there anything I can test with the multimeter? (bought this stuff, now gotta use it somehow...). Else how can I check what is wrong? I believe all is done according to the diagram (but will double check of course...).

SteveMinning · Jul 8, 2012

I had a similar experience. After changing my wiring harness I had a fuse blow while an hour from home. The culprit turned out to be the extremely cheap plastic fuze blocks that they build into the modern harnesses. Essentially the spring hangs up and the vibration of the bike causes the contacts to chatter resulting in arcing.

I fixed my problem by replacing the fuse block with one of those modern auto re-setting fuze blocks. Haven't had a problem since.

You can buy them in various current ratings. Here's a picture of the one I used:

Steve

L.A.B. · Jul 8, 2012

Orsonoce said:
is there anything I can test with the multimeter? (bought this stuff, now gotta use it somehow...). Else how can I check what is wrong? I believe all is done according to the diagram (but will double check of course...).

If the short was caused by a chafed wire or loose connector then it may not occur unless there's some vibration, that's why I suggested doing a visual check in the obvious places (headlamp shell, tail lamp assembly) first, as a meter may not necessarily show the fault.

Guido · Jul 8, 2012

Not being an electrician as I am color blind I have found shorts by process of elimination.
I would disconnect all wires to the lighting systems, i.e. tail lights, stop light switch, wires in the shell.
Install fuse, turn key on to lights and if fuse is still good then the connections in the harness must be fine. But wiggle them to make sure.
Not with the key on to the lights start connecting the lighting systems, i.e. tail light, stop lights, stop light switch and then hit the brakes, front and rear.
Fuse still good? Then that system is fine.
Now go do the head light wires in the shell one by one hitting the brakes after each hook up. I know they are not really connected, it's just something I'd do.
Flip the high beam switch too.
My money is it's in the shell or the ignition switch.

Hobot · Jul 8, 2012

Have a look around after dark tugging bumping stuff. I've had fuse blown from tail light braided Earth lead coming loose so vibration shorted it to power wire. Test light is way more practical-handy than mutimeter for this smoke loss mystery. Try with out various bulbs installed to see if that narrows mystery down.

L.A.B. · Jul 9, 2012

Thinking about this some more, the short could also be somewhere along the headlamp blue/yellow [UY]wire between the Ign.Sw. (terminal 4) and the light switch in the headlamp shell.

Hobot · Jul 9, 2012

Bar switch and lamp clutter confuse me no end but especially in the weird Earth paths so too easy to interconnect to switched power terminal.

Orsonoce · Jul 10, 2012

will give it a try tomorrow evening. will post results.
BTW spent a couple of hours today looking for fuses - no luck. I'm left with one so wish me luck.

L.A.B. · Jul 10, 2012

Orsonoce said:
BTW spent a couple of hours today looking for fuses - no luck.

http://www.vehicle-wiring-products.eu/V ... .php#glass

But you don't have to stick with the old 30mm 35A glass fuses. You can always change the fuse holder to one that takes a blade fuse (15 or 20A) then you should have no problem getting fuses.

Orsonoce said:
I'm left with one so wish me luck.

Use a bulb in place of the fuse, it should help you to locate the short.

Orsonoce · Jul 10, 2012

Use a bulb in place of the fuse, it should help you to locate the short.[/quote]

what you mean w that? why help? would the light get stronger if too much tension go thru the bulb? (bear with me if I'm saying something stupid. as said I know zero nothing about electrics...)
(thanks for the link - will order a dozen straight away...)

L.A.B. · Jul 10, 2012

Orsonoce said:
what you mean w that? why help? would the light get stronger if too much tension go thru the bulb? (bear with me if I'm saying something stupid. as said I know zero nothing about electrics...)

With a bulb in place of the fuse, the bulb will light if there's a short because the short will be completing the bulb circuit to earth/ground.

If each suspect wire or electrical component is disconnected in turn and one of those disconnections results in the bulb either going out, or it noticeably reduces in brilliance then the short is very likely to be somewhere along in that particular wire.

As the fault appears to be somewhere in a lighting circuit after the ignition switch it may be worth disconnecting the white wire/s from Ign.Sw. terminal 2 temporarily before you begin to disconnecting any of the lighting circuit wires.

Brooking 850 · Jul 11, 2012

Direct short to handlbar (earth) in the light control switch can cause grief, I run a band of electrical tape on the bar before clamping the controller together just in case, added insulation.
Regards Mike

Orsonoce · Jul 13, 2012

Bulb test on going - bulb turning on as soon as I set the ignition switch to lights on.
disconnected the tail light - no changes.
disconnected front/rear stop lights, no changes.
tomorrow looking into headshell.
more to come.

L.A.B. · Jul 13, 2012

Orsonoce said:
Bulb test on going - bulb turning on as soon as I set the ignition switch to lights on.
disconnected the tail light - no changes.
disconnected front/rear stop lights, no changes.
tomorrow looking into headshell.
more to come.

If the headlamp bulb is fitted, then under normal conditions the test bulb will probably still light up, but it should not be as bright as normal unless the test bulb used is a fairly low Watt bulb.

One thing maybe worth checking is the single terminal [4] on the ignition switch. It is only fixed by a single rivet so it is possible for the tab to rotate enough to touch the body of the switch.

Orsonoce · Jul 13, 2012

L.A.B. said:
If the headlamp bulb is fitted, then under normal conditions the test bulb will probably still light up, but it should not be as bright as normal unless the test bulb used is a fairly low Watt bulb.

w headlamp fitted test bulb lights up very bright (will check the watt), without headlamp lights up a tiny bit - at that point if I use the horn or press the brakes it goes again very very bright. which is maybe normal (is it?). tomorrow I'll check terminal 4 on ignition switch.

L.A.B. · Jul 13, 2012

Orsonoce said:
w headlamp fitted test bulb lights up very bright (will check the watt), without headlamp lights up a tiny bit - at that point if I use the horn or press the brakes it goes again very very bright. which is maybe normal (is it?). tomorrow I'll check terminal 4 on ignition switch.

That all sounds reasonably normal, if there was a dead short in the system then the bulb should stay reasonably bright. If it's something like a bare wire rubbing, then it might not occur again until there's some vibration or movement.

great ride, fuse blows - Help!

Orsonoce

L.A.B.

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Orsonoce

SteveMinning

L.A.B.

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Guido

Hobot

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Hobot

Orsonoce

L.A.B.

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Orsonoce

L.A.B.

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Brooking 850

Orsonoce

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Orsonoce

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