Blown fuses

[Oggers]

Gents

Bike nearly complete after a modest refresh, but upon connecting up to battery, it blows fuses - the 15A. Neutral indicator lamp glows momentarily, goes out, fuse blown. Tried two more, even a 35A, still blows!

Guess I may have a short somewhere, but I am hopeless at electrics. I do have a multimeter though. Switchgear and headlamp all came apart, so all those connections in the headlamp shell and within the switchgear came apart. I did label them all though beforehand....

Any clues where to start and how to proceed would be most appreciated.

Many thanks

 

[taysidedragon]

Impossible to tell without being there. Go over every connection that has been disturbed and double check that it's connected to the right wire. And check all wires to make sure nothing is trapped or damaged and causing your short.
Normally I would say get someone who knows what they're doing to have a look, but not really an option at the moment. 😕

[SteveD CB500K0]

For a complete novice:

Ignition off.

Multimeter on ohms between fuse and ground. If there’s a short it will show zero or there abouts.

Unplug stuff one at a time and see if this changes. If it doesn’t, plug it back in and move on to the next.

Report back.


Sent from my iPhone using Tapatalk

[Bryanj]

First question
Are you fitting the battery the correct way round i.e -ve to earth

[Oggers]

Gents

Steve - done as you say - zero ohms. There is something across the other fuses though....
Bryan - battery connected correctly

Things I have done since

With ignition on

Lamp across the fuse terminals lights as brighly as it does across battery terminals - I guess it should not!
As an aside, I measured the current draw and it seems to be 0.29A as per battery with ignition on - so why does a 35A fuse blow Forgive any stupidity here!

Shorts inside swtichgear could be an issue. Tested all wires from the hadlebars to the bundle on the frame above the head. Pulled each each one off to see if lamp across the fuse dims or goes out - lamp still lit on each one.

Checked all the wires inside the shell. The seem OK, nothing touching any earth point - apart from the 2 green wires which should earth anyways each side of the shell.

Stumpted - Help please! 

 

[Nurse Julie]

If you look at the wiring diagram and trace which components are covered by the 15A fuse, that may give you a clue. By what I can see the 15A fuse only covers the starter system and its components but my wiring knowledge is not comprehensive 😊😊😊

[TrickyMicky]

If I may suggest a possibility?  A couple of years ago I had a similar situation with the main fuse blowing, but the bike was being ridden fairly frequently, and I had not disturbed anything electrical. I was advised to look closely at the blown fuse, if the fuse wire has parted in the middle of the glass then that indicates a short circuit. If the fuse wire has parted company from one of the end caps, then it has got warm because it is having difficulty drawing enough current. This was what was happening in my case, and I was advised to remove the fuse holder and locate the white multi-plug behind it, pull the plug apart and inspect the terminals inside. Lo and behold, after 40 years of use they had all turned a beautiful shade of GREEN! Half an hours work with a set of small jeweller's files got them all nice and clean, re-assembled and weather proofed, and no further problems!
    PS. Before diving into the terminals with the files, make sure you have taken the earth lead off the battery! Regards, Mick.

[Bryanj]

How many fuses are there 1 or 3(not counting spares)

[Nurse Julie]

3 Bryan. The 15a, and 2 x 7a
The 15 is the main and the 2 7A are for the Headlight and Tail light.

[mike the bike]

Does it blow with the other fuses (7A) removed?

[Bryanj]

Disconnect ignition switch and see if it blows then

[Oggers]

Gents

Many thanks for all your kind replies - to answer

Disconnect ignition switch - Fuse only blows when ignition turned on.
Blow with other uses removed? - Don't know, haven't tried, but other as fuses are a separate circuit, i imagine it  would
Switchgear wiring - My prime suspect, but I did disconnect all of it and the lamp still lit across the fuse terminals. I'll try it again though...
3 fuses 2 x7A 1 X15A
Fuse holder etc - yes , i'll take a look at it. Could be short behind it/on it.

My basic plan is to place the tail lamp across the fuse terminal, ignition on, and just go through stuff until it goes out - or dims considerably. Bike all worked fine before disassembly, so I am thinking it can only be electrical stuff that I have touched! Switchgear mainly.....   

[Orcade-Ian]

Hi Mark,
Your bike is a US import which would once have had daytime running lights at the front with twin filament indicators.  Have those wires from that system got mixed up with some others, especially earths?  Can’t remember the colours of those though.

Ian

[Oggers]

Gents

Back to basics I feel, and in order to substatiate my thinking - or not as the case may be!

Why does a 35A fuse blow when ignition is on! Not getting that at all. There is nothing in that fuse circuit pulling that much amps just when ignition is on and nothing energised - like starter or some such.? If there is a short somewhere, then it surely would not blow a 35A fuse?

Is my theory of the tail lamp being brighly lit when ignition is on a true indication of a short? If ignition is on, there would be power across the fuse anyways...

Deeply confused....

Ian - Hello! I knew I shouldn't have fiddled! I'll check all the wiring in the shell - again - but it was all labelled up and went back the same way. headlamp and the wiring connector are currently off the bike...

Incidentally, when ignition tereminal connector is pulled, light goes out - which to me is hardly surprising as I am thinking the ignition swtich is the feed latch for the fuse. Does this indicate anything else though?

[Bryanj]

Somewhere a wrong wire is connected to a black wire OR a black wire is trapped.
To sort this you need to be VERY methodical.
 Disconnect everything yes i mean EVERYTHING Take mutimeter set on low ohms and check reading when leads connected together, treat this as zero. Connect the black lead to a good earth and start testing with red lead first to all red points then turn ignition on and all black points.
Report back as full procedure to much to assimilate in one go.
You should be seeing infinite resistance(super high)