I had similar issues with my '43 M20 dynamo, also a E3HM. I tried everything. After passing all my tests, except for the ability to generate 6v+ DC, I sent the armature to White Armature in Wisconsin US. They rewound it, balanced and trued the commutator on a lathe. Two armatures cost me about $100 US, and about 3 weeks wait time. Runs fine now, and I use an electronic regulator.
The technician, who works often on Harley Davidson generators, said the most common armature problem is the commutator is not machined true with the armature core and axles. The brushes don't maintain contact, and the assembly works intermittently, at best.
Richard I did all the tests you did with similar results on the dynamo of my 5SW, although mine did motor, but nothing when I spun it. I phoned up Paul in Shaftsbury for some advice. He said straight off, "Your armature is knackered" I said "Yeah But, No But".... He said "NO BUTS! It's your armature! So I bought a new one off him for 65 Quid and it all works fine now.
The truth is, we haven't got the the required full equipment for testing ie 'growler' and such. Ron
I flashed the field to get some magnetism back into it and it did spin up but quite slowly. I will try some new brushes that I have coming, if its still poor it will have to be a new armature¬
New armature it is then! Just as a check/confirm, I need a 200304 armature and it will fit in the E3HAC33-0 body I have ?? (I found out I had a 200303 armature in the one I have - with wrong drive end).
Richard.
