Author Topic: Peculiar charging issue  (Read 348 times)

Offline bikerbob

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Peculiar charging issue
« on: 22.05. 2019 15:42 »
I have a 1956 swinging arm A7 6volt system, dynamo overhauled about 18 months ago it has a toothed belt drive with DVR2 regulator and a Cyclon battery.   The last couple of times that I have been out the ammeter has been showing abnormal charging, regardless of wether the head lights are on or off or what speed you are doing 55mph or 5mph the ammeter will suddenly go from a slight charge to about 5-7 amp charge then seconds later go back to normal this happens suddenly the needle does not move gradually up or down but instantly. This is not normal and as I say it has just started recently up until then everything was normal riding with the lights on at anything over tickover you were charging slightly and on tickover with the headlight on you got a slight discharge. So anybody got any ideas as what is the cause of this sudden change.

Online Greybeard

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Re: Peculiar charging issue
« Reply #1 on: 22.05. 2019 16:03 »
I wonder if the problem is a mechanical one inside the ammeter; they are not exactly precision instruments. Do you have an alternative ammeter you could try?
I have an old one here you can borrow if you like.

Offline bikerbob

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Re: Peculiar charging issue
« Reply #2 on: 22.05. 2019 16:15 »
Thanks for that offer but I do have an old one in the garage somewhere will give that a go but sadly because of other committments will not be able to work on the bike till next week.

Online groily

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Re: Peculiar charging issue
« Reply #3 on: 22.05. 2019 17:28 »
One possible line of inquiry  . . .

If you have anything wired directly from the battery - eg horn or brake light - then when you apply them, the ammeter will show a chage as the dynamo compensates for the load on the battery. It does it in the blink of an eye. In fact it's how I know my brake lights actually work - or not!

So  . . . if there is a short, or funny fault, on any item that is not wired via the ammeter, you would get sudden charges showing there's activity (maybe unintended activity) - which is making the dynamo think it needs to provide a boost.

If you do have the brake light coming straight off the battery, I'd start by having a good look at the brake light switch, and the wiring under the rear mudguard. These wires are horribly notorious for chafing: I refuse to run any wire under any mudguard EVER - and sod 'original', along with the bendy tin retaining tags that break. And then the horn (if also wired direct). If there aren't fuses in the circuits, I think I'd go there, just in case something fries itself.

If it isn't a 'load' that is causing the needle to flutter, then unless the ammeter is defective (it's always tempting, but often wrong, to blame the tools - my old dad always said warning lights were just one more possible point of failure -and it usually cost him dearly), it could be there is a short in the dynamo end cover, or or or   . . .  sadly, there are far too many potential  'ors'.

But you're right, it ain't normal. And I bet the ammeter is telling the truth, or at least partly.
Bill

Online chaterlea25

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Re: Peculiar charging issue
« Reply #4 on: 22.05. 2019 18:21 »
Hi Bob,
Another suggestion that may be relevant??
Does the bike have wired earths to the headlamp, tail lamp and then to the battery and regulator ?
Agree with the other suggestions to try another ammeter too
If the charging was surging as described it would show as a noticeable change of brightness of the headlamp

John

1961 Super Rocket
1963 RGS (ongoing)

Online metalflake11

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Re: Peculiar charging issue
« Reply #5 on: 22.05. 2019 22:18 »
A quick simple possibility to check, is the earth from the regulator. (black wire I think) They will sometimes cause surging if the earth is bad.

They will also stop working altogether if you allow them to run like that.

England N.W
1960 A10
England

Online duTch

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Re: Peculiar charging issue
« Reply #6 on: 22.05. 2019 23:53 »

 How good is your battery ?......I'm having a similar issue but a replacement mechanical reg which is crap quality and needs (more) adjusting but does at least kinda work but the LED lights flicker, and the battery doesn't hold much charge.
      I won't hijack your story but will as John suggests, check inside the dynamo end cover, as I had short there and I ended up with a fried battery.
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline bikerbob

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Re: Peculiar charging issue
« Reply #7 on: 23.05. 2019 09:20 »
Thanks for those replies and next week I will check them out I did rewire the bike a couple of years ago but  apart from putting a fuse in directly off the battery it is wired as per the original BSA wiring diagram. The battery is only about 18 months old and checks out OK.

Online Slymo

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Re: Peculiar charging issue
« Reply #8 on: 23.05. 2019 11:14 »
Mine does that when I apply the bake brake. The brake light doesnt show a discharge through the ammeter but the compensating charge is shown.
NZ

Online ironhead

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Re: Peculiar charging issue
« Reply #9 on: 24.05. 2019 00:00 »
Mine does that when I apply the bake brake. The brake light doesnt show a discharge through the ammeter but the compensating charge is shown.

same here
SA

Offline bikerbob

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Re: Peculiar charging issue
« Reply #10 on: 29.05. 2019 10:29 »
An update on my problem I checked all the earths and have good continuity. When I came to check the ammeter I noticed that one of the terminals was loose so with the lights on if you moved the terminal  the lights went on and off so I have ordered a new ammeter, hope this is the problem. Never got to try the spare ammeter  because it is not in very good condition even though it works so need a new one anyway.

Offline bikerbob

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Re: Peculiar charging issue
« Reply #11 on: 07.06. 2019 14:25 »
Update new ammeter arrived today fitted and now all appears to be working ok so Greybeard you were right in suspecting the ammerter which had a loose terminal thanks for all the responses.

Online Greybeard

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Re: Peculiar charging issue
« Reply #12 on: 11.06. 2019 09:37 »
It's easy to overthink a problem