The best reference is a small booklet by D.G. (Harry) Hales 'The Austin Seven Electrical Guide' printed by Smallprints (no date)

This covers Dynamos, cut outs and switch panels including the 1922-1928 DF and DFL Dynamos and offers some helpful information.

I only have a photocopy of this most useful booklet- someone may have an original with clearer pictures.

Cheers, Tony.

Location: Melbourne. Victoria, Australia.

Do these differ much from the DEL? is the 3rd brush adjustable?
With two ball races care is necessary that not preloaded or constrained.
For those familair with more common 2 pole devices the 4 pole can be puzzling, with main brushes at 90 deg. And armature not wound 1 to 2 to 3 but 1 to mid to 2 etc whch complicates tests with an ohmmeter.
The modest output best taken from the no load ammeter charge; balancing lamps is only applicable with original wattage bulbs.

Location: Auckland, NZ

Bob.I'm no dynamo expert but my rebuilt CAV dynamo was capable of producing 27 amps unregulated.The third brush is adjustable and the bearing located in the aluminium die cast brush end can slide in the housing.
This light aluminium casting is usually cracked,or the bearing dia oversize.

Thanks A i S.
That output is surprising but, in the modern jargon, “not sustainable”!

I have done all my own car work on various troublesome makes over the decades. I have no trade background but managed to avoid many of the provoked failures in which many “professionals” seem to specialise.
But I did manage to ruin a bearing on a DEL dynamo....

Location: Auckland, NZ

I am also after a copy of this booklet. Does anyone have a copy? Has it been reprinted? Can anyone copy their booklet to the web site?
Thanks in anticipation.

Location: Findon West Sussex

Thanks to all who have contributed to this thread. I got enough information to determine that both my dynamos were beyond a quick fix for our trip to France next week. I dipped my hand in my pocket and bought a tested working dynamo.

Location: just north of Cambridge