Dynamo woes

[David Stepney]

Yes, if your car is negative earth, then my instructions should be reversed. However, I think your car should be positive earth. I am under the impression that the cars changed from negative to positive earth upon the introduction of the Ruby in 1934, but I am happy to be corrected on this.

Sorry to correct you David but I think the change to positive earth was a bit later. Looking in 'The Austin Seven the motor for the million' R J Wyatt tells us that Ruby production started in July or August 1934, but the polarity change was introduced in December 1935.

My Ruby has always been negative earth, first registered December '34.

Thank you Andrew. I wasn't sure, and I didn't have my copy of Wyatt to hand when I wrote my post

[AustinWood]

I don#'t have a modern car and our 1929 fabric saloon is my everyday car. The dynamo hasn't worked for about a year. We use a battery conditioner which is plugged in when it's in the garage which keeps the battery topped up.
A fully charged battery should keep the car working for at least 500 miles in daylight. We have LED bulbs which mean that night driving isn't an issue either.
If the dynamo was working I wouldn't use the conditioner. The standard set up tends to overcharge the battery.

[Austin in the Shed]

I'm no electrical expert but have a friend who is.The A7 dynamo in good order is certainly up to the job but it's usually the regulator that doesn't perform as well.

[Tiger]

Hi I don’t think that the original A7 set up had a regulator.

The charge being controlled by the lighting/ignition switch.
However many will have been updated since.

[JoeRowing]

So the dynamo came off today and I found some broken wires inside and the commutator has seen better days. my guess is it hasn't worked in an age!

What/who's the best source of a new one?

[Ian Williams]

A lot of dynamos are rebuildable Joe, try re connecting the broken wires and testing the windings, if they are good it should work. The commutator can be lightly skimmed in a lathe, bearings replaced if worn, watch out for the little cotton reel type insulators on the brush spring posts, they go brittle and break are often missing causing a short and on a faulty dynamo are sometimes the only reason it wont charge. I would have thought Tony Betts would be a good source of a replacement unit or parts if you need them. There were people like Vince Leek who rebuilt them on exchange basis, not sure if anyone still offers this service in the UK.

[JoeRowing]

an exchange replacement would be ideal as I think the commutator needs a skim

[Alan]

Google Armoto in chesterfield