Dynamo brush replacement

[PeterN]

Two questions relating to the C35A dynamo please
Is it possible to replace the brushes with the dynamo in situ.
Is it possible to remove and replace the dynamo without losing the timing

Thanks for advice

[Alan]

It’s like a lot of Austin 7 things. The answer to both questions is yes, but it’s so much easier the other way. Regarding the timing, when I remove the dynamo what I do is turn the engine on the handle until the points are just opening on number one. Remove the dynamo to do whatever to it and be very careful not to turn the engine any. When you put it back just make sure it’s just opening the points on number one and you are good to go.

[David Stepney]

I have a slightly different approach. I have marked my flywheel with a line of centrepunch marks 1 and 9/16 inches before tdc. (That is to the left of the 1/4 tdc mark on the flywheel when the engine is viewed from the rear). This equates to 20 degrees before tdc, which is the fully advanced timing. If I have to disturb the dynamo or distributor for any reason, it is a simple task to remove the flywheel cover, align the row of dots with the rear block securing nut, make sure the advance/retard lever is fully advanced, and arrange the distributor so that the points are just opening. It is possible to get the timing 180 degrees out,(been there and done that) but it is then just a case of rearranging the plug leads.

[bob46320]

I used to make a sketch as to where the distributer arm was before removing the dynamo and just re-engage in same position (without letting the engine turn) - easier these days with cameras on your phone.
From memory, Don't forget that you may need a long box spanner to undo the (1/4" ??) dynamo bolts from the timing gear housing.
Also be prepared to replace the small insulating bushes that hold the brush support arms - they sometimes get very fragile in old age!

[Chris KC]

I do it the same way as Alan.

[Steve kay]

Whether it has to do with stages of the moon, alignment of the planets or Sods Law, I reckon that we are 180 degrees out three times out of four. However, being expected it is but the work of half a minute to correct it and immediately it fires up.

[PeterN]

Read and taken note of. Thank you each.

[Alan]

If you are looking for fully advanced position then aligning the tdc mark with the oil pressure gauge take off isn’t far wrong.

[Colin Cooke]

Hi All,

Hope this is not straying off topic too much. And I apologise if this specific question has been answered elsewhere.

I have just fitted a C35M dynamo, assembled from a bag of bits, new brushes with turned down and hacksawed commutator. I've got a cutout from a 1937 A7. 

The minimum charge on the ammeter is 8amps. Summer setting and third brush pushed to the top. As I've got new brushes, I'm concerned that this might get even higher, as they bed in. I would like to run with 1 or 2 amps on Summer, and maybe up to 8 amps on Winter. Any ideas what I have done wrong?

My previous dynamo, had just enough charge to make sure the red light went out. Adjustment of the third brush sent the charge rate directly from very small to 14 amps, as shown on the ammeter. Battery always seemed to have enough oomph in it, but felt I wanted to try a different dynamo.

Finally - what happens when the wires on the dynamo are fitted the wrong way round?

Appreciate any help you can give. Not too worried, but got Nightjar rally tomorrow, so about 5 hours of night running.

Regards,
Colin