Vintage Minor Register

Nick,

Going back to the question about the half charge resistor, I just re-read this in the Dynamo Electrickery article in our Magazine M 127:

"So where is this resistor to be found? That depends on your particular dynamo. Some dynamo field
windings have the resistor wire buried within the cloth-bound coils rendering it invisible. On other dynamos, the
resistance wire can be found taking the form of a ring of bound wire sitting on top of the four field coils. When
Roger Lucke first had his car, fitted with a DDS5 dynamo, it would not Summer Charge. Search as he might, he
could not find the half charge resistor, until he found the burnt out resistance wire sitting on top of the field
windings in the dynamo itself. This he replaced with an external 2.2 Ohm, 50 Watt resistor, connected between
the +D and F terminals, and - hey presto - it worked! Should anyone need one, it is a R.S. Ltd part number 158-
317. Cost about £2."

I had the same problem on the Austin and I fitted an external resistor but mine was a 1.5 ohm 50 watt, wonder what the difference in charge rate is between a 2.2 ohm and a 1.5 ohm??

Would this equate to the curly wire in the terminal box on sv dynamos? My car had a piece of 2.5mm copper household wire in its place which eventually led to the dynamo burning out and i'd always wondered what would replace the wire if it was missing!?

Yes, that's the resistance wire for the SV C45 dynamo. Some SV dynamos had the resistance box, and some didn't - having the resistance inside and just a Bakelite terminal block in the top of the dynamo.