Lucas C40 Question

[Jon J 1250]

Calling all dynamo experts!

I have two 1966 Lucas C40’s

One works, generates 13+ volts and runs as a motor when connected to the battery, the other does nothing apart from a bit of sparking on the brushes.

I have checked continuity and both are the same, and they both have the same resistance reading on the field coil.

When testing the segments on the commutator there is continuity between every segment, which is odd as I thought they were all separate windings and you only get continuity between each segment and the one directly opposite it.

I’m confused, in my book they both shouldn’t work if the above it true, but one does and there other doesn’t.

Can anyone with more knowledge enlighten me?
 

Cheers

Jon

[johny]

no, the armature winding is a wave type looping in and out of each communtator segment. If theres an open circuit the segment is still connected to the winding so difficult to measure the small change in resistance with a multimeter but nevertheless it wont work... 

[Jon J 1250]

1 hour ago, johny said:

no, the armature winding is a wave type looping in and out of each communtator segment. If theres an open circuit the segment is still connected to the winding so difficult to measure the small change in resistance with a multimeter but nevertheless it wont work... 

Thanks, makes sense know why I can’t find a fault.

[johny]

Unusual for it to fail unless it looks or smells burnt? You could try cleaning the slots out between the commutator segments with a pin or similar as a carbon build up here can short them. Also of course both the armature and field coil have to be earthed to the case one side of each respective winding...

[Jon J 1250]

19 hours ago, johny said:

Unusual for it to fail unless it looks or smells burnt? You could try cleaning the slots out between the commutator segments with a pin or similar as a carbon build up here can short them. Also of course both the armature and field coil have to be earthed to the case one side of each respective winding...

I cleaned out all the slots with a jewelers screwdriver, there's no burning or smell, both armatures look identical apart from the one that works being more worn.

I guess there's a break or short somewhere, but you can't see it. I guess that's it, no more can be done.
I am going to swap the working armature into the other shell to keep the 6/1966 date, its for my dad's mint 1966 Mini, where having matching dates, really counts.

Thanks for help.