dynamos

[win]

I am trying to test a dynamo,
Connected a low wattage 12V bulb from F and D to earth lights very dim, checked voltage, 10 V on digital meter.
The field resistance is 6.5 ohms, I have flashed this F positive to earth.
D to earth .9 ohms.
Commutator bars to each other .4 ohms and clear to earth, and are clean and bright.
The brushes look OK are free to slide, spring tension OK.
D brush is clear to earth, the other brush is earthed.
Connecting D+F to a headlight bulb and earth does not light.
When D+F connected to a battery, it runs as a motor.
Put a horse shoe magnet on armature, can feel very very slight movement on 6" rule opposite magnet.
Dynamo does not charge when connected to car.

The above tests I believe, point to a faulty armature, but I have had several other dynamos donated,
they all show similar tests result, can the all have faulty armatures, or am I missing something.
I remember as an apprentice many years ago using a grower to check magnetism of armature.
One old electrician used a 240v motor stator coil to test armature magnetism?
Can anyone help? I am not an electrician
Kind regards Win

[svenedin]

I am no electrician either but this booklet covers all the tests you could need. It includes batteries, coils, dynamos, alternators, starter motors, control boxes, wiper motors.

As well as being available in print form if you search for "Lucas XIA116 Fault Diagnosis Service Manual" you should be able to download a copy for free.

Stephen

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[win]

Thanks Stephen, I have not seen that information.
Regards Win

[svenedin]

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[KeithL]

Thank you @svenedin. A very useful document.

[geoberni]

Yes, that's a useful manual, though it is geared towards establishments with a level of equipment beyond the typical DIY set-up.

I find this one a bit easier to use, aimed at the small garage owner with no electrical knowledge, but likely to have a multi-meter to hand.
Lucas Generator and Control Box Tests.
Lots of downloads of it around, but this one is in colour and a bit cleared than some copies.
I wish the MMOC had such a useful level of technical resources as many smaller marque clubs seem to have, but that's a different topic entirely.....

https://www.mgcc.co.uk/t-register/wp-co ... _Tests.pdf

[oliver90owner]

First check is to see if it motors, when connected to a battery.

[win]

First check is to see if it motors, when connected to a battery.

When D&F connected, it runs like a motor.
Win

[myoldjalopy]

Briskly?

[win]

Briskly?

Approximately 1000 RPM
Regards Win

[myoldjalopy]

OK that seems fairly 'brisk'. I only mentioned it because I once had a dynamo that failed to charge but would run as a motor, albeit sluggishly and erratically.