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Charging issue, on Vitesse


daverclasper
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Hi.  I have hopefully diagnosed this as the dynamo, as with a connecting wire between the 2 dynamo terminals give rapidly fluctuating readings of between 4 and 6 volts.

Apparently these readings point to the armature being damaged, maybe by the control box cut out contacts not opening and battery charge going into the armature.

My ignition light is on at rest and with the engine idling, so maybe I can assume the cut out is currently working?, before I replace the dynamo.

Anything else I should look out for in control box?.

Thanks, Dave 

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Normally what happens is the brushes wear down and start to make poor contact with the commutator so theres still some power produced but its not very stable. This worsens over time and normally results in burning of the commutator (beyond repair?) and no charging..... The field coil can easily be tested for continuity resistance to earth (5.9 +/- 0.3 ohms) while the armature has to be tested across each pair of commutator segments (all should have the same resistance).

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Thanks folks.

I have an apparently recon dynamo, that I picked up for a cheapish price. Will fit that and see how it goes.

If ok, then dismantle the old one to see what's, what.

If there is an ignition light on at engine rest and idle, does that infer the cut out contacts are not staying closed and therefore working at some level?.

Dave

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10 hours ago, poppyman said:

If you connect the dynamo to a battery just with bits of cable it should run like a starter motor but very slowly.... If it runs? it's ok if not? it is kapput.

Tony. 

I prefer the WSM test using a voltmeter to measure the dynamo output with the engine running to prove its working.... 

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Hi,

 An A127 is as good replacement alternator up to around 80A on a single pulley I believe.

Make sure its machine sensed. i.e. the two B+ terminals are shorted internally or externally together. The alternator to battery feed cable will work but a parallel cable will allow more loads to be added without visible volt drops.

Cheers,

Iain.

 

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  • 4 weeks later...

Hi. Have fitted the recon dynamo.  The voltage, direct from dynamo, is reading similar to the old one.

It looks like it has been reconditioned, in that it all looks very clean/new through the back cover, the bearing felt looks new, I think I can see the brushes extending about 10mm from the top of the carriers. The 2 screw heads are a bit mullered, though maybe they use the old ones?.

The field coil resistance is 6.3, measured with dynamo fitted. Is this a tad too high to make much difference?.

Could I be doing something wrong, when measuring the voltage?.

Thanks, Dave   

Edited by daverclasper
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