The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Rick Rybicki on 07.05. 2023 10:52
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I've already posted this on BSAOC forum in UK but had had no definite results so far. There was a suggestion that there's a guy called "CheeserBeezer" out there who is a wizard at this sort of thing. Hope you see this.
I'm running a quite non-standard '59 A10 and it's stopped charging the battery. What's happened so far;
Was working fine but while I was sorting out a problem with rear light I found that the battery wasn't charging from the dynamo. It charges fine from a charger.
Checked the output of E3L dynamo and it was showing about 1.6v.
Checked resistances, F---3 ohm, D---0.6 ohm. OK.
As the bike hadn't really been used for a few months I decided to "flash" the dynamo.
After the "flash" I tested the output again and now it's showing a NEGATIVE output of about -1.6v.
The dynamo was professionally rebuilt some years ago by Dave Lindsley but has only done about 3k miles in the last 7 years.
It's set up through a 6 - 12v conversion regulator, negative earth and driven by a "Hawker" geared up belt drive.
Help!!! How do I fix it???? Please give any answers in the simplest of terms!
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Are you joining F & D together, to test voltage between them and the case?
And revving to midrange?
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Thanks for the mention. There's a dynamo test page on my website. I suggest you use that s a starting point
https://sites.google.com/site/priorymagnetos/dynamos
You need to make sure you're spinning the dynamo fast enough to achieve the output you're looking for. A 6v dynamo produces about 9v @1500 r.p.m.
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Are you joining F & D together, to test voltage between them and the case?
And revving to midrange?
Yes.
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Are you joining F & D together, to test voltage between them and the case?
And revving to midrange?
Yes.
Try cleaning the commutator, brushes can have too high a resistance and this prevents “self starting” of the dynamo, even when armature resistance measures ok.
At the risk of confusing, if you (alternatively to the F+D join test) put a current through the field coil and measure the armature voltage (or better still put a headlight bulb across the armature) that can give a better indication of the health of a dynamo.