Hitchcocks Forum

I have been riding my 500 twin on the road at last - all pretty good but had an electrical problem today. All lights went off but being a MagDyno the engine ran fine. I rode a short distance home. Checking things my fuse was fine but the battery was warm. I had noticed the ammeter was reading high during the short ride home. I noticed in testing that the lead to the battery +'ve terminal gets warm when connected. Am I looking for a simple short somewhere or something else? The bike is standard but a solid state +'ve earth regulator/rectifier. Any ideas most welcome.

For a start, look for a loose connection or broken wire in the loom. May God have mercy for you.

12 volt or 6? And if 12, how was the conversion achieved? Rewired dynamo or in the regulator? REgards, Mark

If you connect the earth + it would be sparking when touching the terminal if it gets warm.
Sounds like a short somewhere.It would show a strong discharge surely.

Over the years I've known two occasions when the ammeter itself was shorting out. I first had it many happen years ago in the mid 1970s (I was about 18 years old) on my 1964 BSA C15 and the ammeter itself let some of its smoke out. I got the bike home by taking the ammeter out of circuit (just a matter of disconnecting the "negative" terminal and fitting it on the "positive", above the existing wire.

Not long afterwards, riding that same bike, I came across a perplexed bunch of rough looking mature riders (Hell's Angels), on very smart Triumph and Norton specials, stopped in a gaggle around one bike at the side of a country road in Derbyshire. As I always carried some tools (I had to, my bike was a BSA) I stopped and asked what the problem was. The Triton rider (looked like the bike was a very new special) had suffered an electrical failure, with smoke coming out of the bike's headlight! I told him I thought I might know what the fault was and might be able to fix it. The group were a bit scathing, but I got my tool kit out, took out the headlight unit, showed him the very much overheated ammeter (plastic case partly melted) and had the bike going again in two minutes. They were so impressed they didn't bother to beat me up and just rode off without saying thanks!

So - I'd say check if your ammeter is ok.

Thanks you all for the replies. Mark M - I have kept the bike using 6v. Wheaters - you could be right there is evidence that the ammeter was slightly fried in a previous life but it was working in that state until now. I am wondering if using the bike I have gone over a bump and something has moved. I only rewired what I needed to during restoration I am now suspect of wiring left from before. I see Hitchcocks do a wiring loom I might try that (being lazy) as I also want to fit a front brake light switch and could kill two birds with one stone. Am I likely to have damaged anything?

Similar thing happened recently with my 1958 Meteor Minor which works off an alternator. For an hour or so the ammeter had been showing a strong charging current, then the electrics died, in the middle of nowhere. The battery was distinctly warm and when I removed it later it was bulging. Turned out to be a faulty (6v, positive earth) modern solid state regulator rectifier.

ed.lazda that is really interesting. Is there an easy way to test if my regulator/rectifier is at fault anybody?

Your magdyno won't use a reg/rectifier as the dynamo's output is DC, not AC (that's alternator territory). Standard Lucas kit to go with the dynamo of the period would be the CVC (voltage controller) unit normally situated under the saddle. You can get solid state electronic DC regulators which will fit in the CVC housing, but as ed.lazda's post shows, modern devices can fail too.



Meanwhile this might be of interest:



https://matchlessclueless.com/electrica ... regulator/



So might this:

https://www.bt-h.biz/alton-generators-7-c.asp



A.

Sorry, I misread your original post, I see you **have** an electronic regulator instead of the Lucas CVC, but it still should not need any kind of rectifier unless you've fitted an Alton generator instead of the Lucas dynamo. Reg/rectifiers can usually be wired for positive OR negative earth.



What make/model is your electronic regulator?



A.