charging problem is driving me mad

[admin]

This has been going on for 2 weeks now, off and on.
It is officially driving me mad.

standard lucas magdyno driven bike, short dynamo, 6v lead acid battery. nothing unusual.

I cannot get it to charge
bike running. lights on. Ammeter shows discharge (battery shows discharge) lights do not get brighter.
It was always ok before but hasn't been run for ages.

1. I changed the tiny 6v battery for a new one. No difference
2. The short dynamo will run my AVOmeter up to 20v and also directly light a 12v 55w bulb. I pulled it out and cleaned it and everything seems fine. I couldn't turn the magneto fibre wheel against the engine - I assume if it lights a large bulb and the driving wheel cannot be moved then it's good.
3. I have tried three regulators. two electronic and one mechanical
4. The mechanical regulator follows the dynamo output when I clamp the AVOmeter to it's frame - this tells me that the wiring from the dynamo to the regulator is ok.
5. I have checked every wire for continuity and resistance ESPECIALLY the one from regulator to headlamp and switch
6. The bike is wired as it should be - regulator to switch terminal, switch terminal to ammeter, ammeter to battery

I do not get any output at all on the regulator to ammeter wire (when disconnected inside the headlamp) - this really confuses me.
Should I be able to pull the fuse from the battery and the charging system run the lights ??

I can try another dynamo,

please help ....

[brenton.roy]

Hi John,
I expect you have covered these, but I'll ask anyway.
Is the gennie getting an earth to the frame?
Have you tried bypassing the ammeter?
Sorry, I'm crap at electrics..

[Simon.Gardiner]

John:
I've also spent a lot of time trying to get a dyno to charge. Like yours, it passed all the usual 'easy' tests (as well as the light bulb test I checked continuity/resistance around the commutator segments and for the field coil, and 'motored' it - all fine) but it just wouldn't come up with the goods on the bike.
Out of desperation I gave the dyno a full rebuild - and it was perfect from the minute I connected it up (well, after I'd got the brush/field coil connections corrected).
I assume there was a load-related issue somewhere as I don't think any of my the tests actually reproduces the current draw 'in action'.
Sorry, not a lot of help, maybe some encouragement to swap the thing out next!

SG

[alan.moore]

John, just a thought I have read on the forum somewhere that dynamos can change polarity when left for a long time. Whilst you have a good output from the Dynamo maybe it is the wrong polarity for your setup? just a thought

Cheers
Alan

Edit....so as Steve says below maybe flash it to make sure the polarity is correct

[Steven.Carter]

Probably needs a flash. they can loose their residual magnatism.
Steve

[admin]

The dynamo puts out charge on the bike - so it's operating in the right rotation, It's been flashed so many times it must hurt...

When you jumper D&F, through a bulb, to the engine (earth) it produces enough to light a 12v 55w bulb - so it's deffo earthed.
A mechanical regulator shows charge too when I put the meter on it's chassis (it's how I usually adjust them).

I take the point about ammeters and changing the dynamo - I have known working dynamos on other bikes that I can substitute in.

[alan.moore]

Assuming the system is negative earth I was just wondering whether, if the polarity had changed, it was putting out positive through the dynamo body and negative through the wire to the regulator. It would still light a bulb and you would still get voltage ..just the wrong way round. But I suppose the voltmeter you are using would then show a negative value if you have the black test lead connected to earth.
Cheerrs
Alan

[admin]

Assuming the system is negative earth I was just wondering whether, if the polarity had changed, it was putting out positive through the dynamo body and negative through the wire to the regulator. It would still light a bulb and you would still get voltage ..just the wrong way round. But I suppose the voltmeter you are using would then show a negative value if you have the black test lead connected to earth.
Cheerrs
Alan

Anything is possible at this stage .. it's been in and out, jumped, tested and fiddled with for hours.
Thanks Alan ..

[adrie.degraaff]

Or the sprocket slip is slipping like my 1956.

[bill.bottrill]

John,
I've read through your post and it seems like you have been very thorough checking out the wiring,I like what alan moore suggests about the dynamo it is obviously giving a good output but is it of the right polarity.
Have you checked out the earth wire from the mechanical regulator to earth, does it connect not just to the frame but to the battery earth as well,you could use a buzzer to check it,this wire helps pull in the relays in the reg box,if it was broken the regulator cutout wouldn't pull in, I checked through and you don't mention it you have F-field A ammeter D -dynamo armature E -earth