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Dave Lid
The Black Country UK
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Dynamo not charging
#760168 12/23/18 4:49 am
Joined: Aug 2016
Posts: 73
BevanC Offline OP
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Hi folks,
The E3LM dynamo on my 1950 VB is not charging. I have video evidence that it was charging before it was shipped from the U.K. to me here in N.Z..

The bike is positive earth; the resistance between the dynamo body and a frame bolt is 0.2 Ohms, which is the same as I get when I short the leads of my multimeter together, so i think the earthing is o.k..

I have followed troubleshooting guidance given on the "matchless clueless" website and have made the following measurements:
- Field terminal to earth resistance = 3 Ohms; Dynamo terminal to earth resistance = 4.3 Ohms
- With the F and D terminals shorted together and the engine idling, I measure around 0.2 V between the terminals and earth, which doesn't seem to change much if I increase the engine speed a bit.
- I have tried flashing the field coil, but no change in voltage readings.
- I have removed the brushes and lightly cleaned the commutator (it wasn't particularly dirty). To my inexperienced eye, the brushes and commutator appear o.k.

A Lucas manual I downloaded seems to suggest the trouble is with the field winding, but the resistance I have measured is the same as that on my Panther's E3LM dynamo, and it works perfectly.

I'm not sure what the next troubleshooting step should be.

Any guidance would be much appreciated.
Cheers,
Bevan

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Re: Dynamo not charging
BevanC #760183 12/23/18 11:33 am
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Is the dynamo turning with the engine? There is usually a clutch and a fibre gear that can go funny.

If it does turn, you may find that a ten mile ride will get it working.

Or-
Connect dynamo F and D together to a spare headlight bulb. Connect the bulb’s common (earth) terminal to the crankcase.

Run the engine at moderate rpm, about 3,000 rpm. If the bulb lights brightly, you have a working dynamo.

If it doesn’t light, try briefly connecting battery live to your joined F&D & bulb while at moderate rpm. That sometimes wakes up a lazy dynamo.

If the bulb does light, check continuity to regulator F and D and also continuity from regulator A and E to battery live and earth, respectively. If it’s non-standard and has an electronic regulator and a switch, then I don’t know the details of your bike.


Amateur Loctite enthusiast.
Re: Dynamo not charging
triton thrasher #760248 12/23/18 9:15 pm
Joined: Aug 2016
Posts: 73
BevanC Offline OP
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Hi, thanks for the reply.
The dynamo is turning with the engine.
It doesn't light a bulb.
I have tried flashing the field coil, as you suggested, to no effect. I'll try a longer ride once the Xmas madness is over.
Hope you have a good one.
Cheers, Bevan

Re: Dynamo not charging
BevanC #760262 12/23/18 10:20 pm
Joined: Jul 2006
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The resistance from D to earth seems a bit high.
Give the rubbing face of the brushes a bit of a rub with a piece of abrasive between the comm and the brush.
Sometimes the brushes get a high resistance film on them.

Re: Dynamo not charging
BevanC #760318 12/24/18 9:41 am
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Flashed the field while the engine is running faster than idle and the bulb is in circuit?

The indicated ohms may not look perfect, but if the field and the armature are not open circuit and not short-circuit, I’d expect some output.

Last edited by triton thrasher; 12/24/18 11:35 am.

Amateur Loctite enthusiast.
Re: Dynamo not charging
BevanC #760856 12/30/18 3:50 am
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BevanC Offline OP
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Hi guys,
Just a followup in case anyone is interested. It was such a lovely day here (29 C), I decided to take the VB for a bit of a ride before pulling the dynamo off. When I returned, to my surprise, it was charging when I revved the engine a bit above idle. Not sure why, since I had tried flashing it etc previously without success, but it now appears to be working fine. Even the old cvc unit is clicking in and out in what appears to be a correct manner.
Long may it continue smile
Cheers & Happy New year
Bevan


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