Morris Minor Owners Club

myoldjalopy wrote: ↑Mon Jan 19, 2026 8:58 am Interesting - I have to say I don't have strong opinions on this either way. I have owned four Minors over the years, one had an alternator and the other three had dynamos. I didn't bother swapping out any of them for an alternate charging system because, even though I generally prefer originality, I wasn't going to faff around changing back to a dynamo. There's always plenty of other jobs to do! The alternator did fail and have to be replaced once, and I have had issues with the cheap control box replacements on one of the cars with dynamos (my current one )

Yes the cheap Far East RB106 control boxes are definitely a weak link in the dynamo system. The RB106 is electromechanical and technically simple but ingenious. It relies on two sets of contact breakers (points) one set of which opens and closes rapidly in use. Unfortunately, rather like the points in the SU fuel pump and the distributor, the points in the RB106 are prone to fouling from dirt, oxidation and pitting which leads to poor or no charging. Various options are available if the original look of the engine bay is desired: new old stock RB106 can be found but they are scarce, the internals of the RB106 can be replaced with an electronic module or there are expensive dynamators (an alternator inside a case that looks like a Lucas dynamo).

Stephen

Can you get +ive earth dynamators?

myoldjalopy wrote: ↑Tue Jan 20, 2026 9:34 am Can you get +ive earth dynamators?

Yes you can:
https://tudorcarparts.co.uk/products/tu ... tor-c39-40

There's also another player in the market place, with a quite similar name :
https://www.autoelectricsupplies.co.uk/ ... lternators

Both also offer 6v versions for people with really old cars....

OK, thanks. Just out of interest, what would be done with the old control box - or would you need something to replace that?

myoldjalopy wrote: ↑Wed Jan 21, 2026 10:23 am OK, thanks. Just out of interest, what would be done with the old control box - or would you need something to replace that?

In terms of electrical connections, using a dynamator (an alternator that looks like a dynamo) is the same as installing an alternator. The RB106 no longer has any role in regulating charging but can either be removed and electrical connections made elsewhere or left as a junction box. For convenience and neatness a small sub-loom can be purchase from suppliers like ESM and this connects to the dynamator/alternator.


Stephen