1955 G9 recommission

[AFSMatchie61]

Back to the electrics, new switch fitted, connect battery and ammeter plunges to the left as far as it will go and stays there, no lights, wires from battery and to ammeter start warming up. Short circuit perhaps? Could it be a regulator problem? The newish reg was on the bike when I got it, maybe knackered or a negative earth unit?
Any ideas?
Thanks!

[MalcW]

Back to the electrics, new switch fitted, connect battery and ammeter plunges to the left as far as it will go and stays there, no lights, wires from battery and to ammeter start warming up. Short circuit perhaps? Could it be a regulator problem? The newish reg was on the bike when I got it, maybe knackered or a negative earth unit?
Any ideas?
Thanks!

Sounds like a short somewhere. I would try disconnecting everything you can and the reconnect one at a time to try and track it down. Good luck.

Malc

[Groily]

Yup, a serious short somewhere, no 'perhaps' about it.

Probably not the regulator though, whether it's correct polarity or not.
Therein hangs a miserable tale though with the Wassell instructions for Neg earth versions, see eg

I have no idea of the vagaries of the things as I have binned any I have come across because I haven't found that they regulate very well compared to some others. This is 'Get What You Pay For' territory.

On the basis that one should always look at the last thing one touched first, have a good look at the switch terminals for position, for clean wiring with no stray strands, and check horn and brake light extra carefully.
You said you had a fuse? Did it blow? If not, where does it sit? Sounds as if even the main battery leads aren't covered by it? If some components aren't covered by it, they are the first place to look - which often is horn or brake light if they're taken straight off the battery and unfused.

Using a meter on the resistance scale with the battery disconnected, you ought to be able to find the unwanted continuity I think.

[AFSMatchie61]

Thanks for the comments chaps, seems the short is in the tail light, disconnected it for now, compounded by inneffective earthing of the bulbs up front, I now have head and side lights - hurrah!
Many thanks again (will watch the vid later Grolly, it is s Wassell unit thats fitted…)

[Groily]

If the hassle is in the tail light unit but shows up with light switch in OFF position, could well be the brake light side that is causing the trouble.
Suggest have a look at the wires under the mudguard if they're still there - it's such a common problem.
Can't stress enough the need to ensure all circuits are covered by the fuse(s)! So many jobs get wrecked by a serious short circuit, destroying new harnesses and hours of work

[AFSMatchie61]

Sorry yes the fuse is now in the blue wire that goes to the black lead from the regulator, will put one in the battery earth lead.
Thanks

[AFSMatchie61]

Well, a few months have passed and I finally got around to starting the bike last week. The electrical short was indeed in the rear mudguard in the most innaccessible place imagineable so I replaced the wires and now all the lights function correctly.
the first start was a bit of an unknown as I had serviced the engine with new filters and so on but nothing more, thankfully it started up on thesecond kick (wow!) and ran very nicely up and down the road, then sat ticking over without any fuss at all. I'll update with pics shortly and perhaps even a video (!)
Thanks All for the hlep thus far.
Cheers

[AFSMatchie61]

The culprit!

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[AFSMatchie61]

And a short clip