Not charging

[Butch (cb)]

When my dynamo stopped working all it needed was a 'reflash'; might that not be the case here?

[Greybeard]

When my dynamo stopped working all it needed was a 'reflash'; might that not be the case here?

I'm not sure he actually has a problem.

[A10 JWO]

I tend to agree with Graybeard, my 1954 A10 has only done 20 miles since the rebuild and has a new charged battery fitted. It has never shown a charge on the amp thing because I have never used the lights. Next time I use it I will run it with the dipped beam like Ninja type people  and see what happens. If it goes flat I will still get home and get straight on the forum.

Regards Colin A10 JWO

[Greybeard]

UPDATE:
I fitted a DVR2 and still have no charge   I may have to apologize to Messrs Wassell & Co.

I think my dynamo must be crook. Using a 12v test bulb,( F & D together, bulb earthed) I sometimes get a nice bright light, other times nuffink. Is it possible that the dynamo is breaking down under load?

I took the end off the dynamo while it was on the bike and cleaned the commutator. The brushes still appear to have enough meat left for the springs to press them to the commutator.
I've cleaned and tested the F and D connection wires on the end cap.

Any advice greatfully received.

[Greybeard]

My dynamo resistances are as follows:
D terminal to earth is 27.5 ohms
F to earth is 3 ohms

[morris]

My dynamo resistances are as follows:
D terminal to earth is 27.5 ohms
F to earth is 3 ohms

Can not confirm your D terminal but F is ok. Service sheet says 2.8 ohms.
I suspect something breaking down under load /vibration.
Could be the field coil shorting internally or earthing. They are pretty fragile.

[trevinoz]

The "D" resistance is far too high.
Have you cleaned the commutator and given the brush surface a bit of a rub?
You may have a high resistance between the brush and commutator. Sometimes the brushes seem to get a bit of a film on the rubbing surface.

Trev.

[wilko]

I've come across intermittent charging in the past and it turned out to be loose field coils.The iron core was tight but the coils surrounding it were loose.

[chaterlea25]

Hi
Digital meters are a PITA doing these tests 
A rough test is to wire a 20w bulb in series with the "D" terminal ( make sure to keep battery polarity correct)
then turn the armature one segment at a time and observe the lamp brightness
an open winding will be self evident

HTH
John

[Greybeard]

UPDATE:
I'm fed up!  I keep thinking aha, this will fix it and it's still the same afterwards. Yesterday I stripped the brushes and backplate, (with the dynamo on the bike). After removing the brushes I checked their rubbing surfaces for resistance and found quite a high value - aha thinks I TrevinOz was right, the brushes have glazed and gotten a high resistance. I gave them a rub on some fine abrasive paper wrapped over a socket to maintain a radius. When they were put back in place but not connected I tested the resistance; brush lead, through armature to other brush lead while carefully turning the engine. I got approx 3ohms and approx 10ohm readings, (I reasoned that the lower reading could be because the brushes were bridging two armature segments - Parallel circuits). After reassembling the dynamo I have 5ohms to earth at the 'D' terminal and 'F' is still showing 2.9ohms. I've flashed the dynamo a few times.
With the engine running the dynamo produces a few millivolts with the correct polarity. It's looking like I need a dynamo overhaul.

[Greybeard]

Just a thought: Would one of you UK based readers have a working dynamo I could borrow?
Of course I would pay Courier costs. The loan would be until the winter arrives and I take the bike off the road. I'm planning to get my dynamo overhauled during the winter at Dave Lindsleys in Leominster. He did a great job on my Magneto last year. He gets the dynamo case replated and everything!

[A10Boy]

Grey
Why don't you give the lads at yeoman's a call, I'm guessing they will have a few decent ones in their shed. Half an hour up the M5.

[Greybeard]

Thanks A10boy I was unaware of these people. I've emailed them.

[Greybeard]

UPDATE:
I removed the dynamo from my bike and took it and my new DVR2 to Dave Lindsley at Leominster; the bloke who rewound and restored my magneto. He put the dynamo on his jig, connected up my regulator and ran the dyno up to speed. At first, no output but when he pressed the brushes against the spinning commutator it started to work. He cleaned the commutator and fitted new brushes. He reckoned, (and I agree) that my old brushes were probably the original ones, ( don't forget that the bike has been unused for 38 years)
I thought I had cleaned the commutator and brushes suffiently but obviously not enough. Worth bearing this in mind if you are having charging problems.
I haven't refitted the dynamo to the bike yet but I have high hopes of a happy outcome!
This work cost me 20 quid. I was sure I was going to need an armature or field coil, or both. He's a good chap is Dave! 

[KiwiGF]

Thanks for letting us know the outcome, i had a similar issue with brushes, except my dynamo would run for a few hundred miles then stop charging, cleaning  the commutator would give me another few hundred miles and so on, cured with new brushes. Its the first thing to check I reckon. In my case the dynamo would not "kick start" itself with f and d joined, but passed all other checks, it would start and keep generating if one put a little current through the field to kick things off. Too much resistance in the brushes was enough to prevent the "kickstart" was my conclusion.

I wonder how many people have bought new armatures etc when the problem was the brushes were faulty!