Morris Minor Owners Club

Hi,
Can I fit a C40 dynamo to my 948cc engine?
I am pretty sure that the old one which has a coil bracket fitted to it is knackered as the ignition warning light remains on with the engine running and the pulley at the front of the dynamo waves in and out as if the shaft is bent!
Thanks folks.

Yes -you can!

Thanks once again BMC, Much appreciated

Try checking the dynamo brushes and the nut on the front of the shaft, or the pulley wheel. New dynamos do not include the pulley so if yours is knackered you will need a new one

I have a new C40 dynamo which is stamped Negative Earth on the casing, is this OK to fit to my Positive Earth car or do I need to make alterations?
Thanks.

Since the dynamo is already neg earth you may as well turn the battery around and convert the car to neg earth. Swap the coil leads over and clean the points and petrol pump contacts.
If you really must keep the car pos earth then just strike a wire from the battery live terminal across the dynamo field terminal.
Don't try converting an alternator folks, you will knacker it.

Sorry Mike,
Can you explain to a thicky this dynamo polarity change procedure involving striking sparks from the terminals?
It sounds a bit dangerous to me, is it as simple as you say?

It is exactly as described......cable from the non earth terminal of the battery - and spark it against the small terminal on the dynamo a few times.

Go for the neg earth option, you get less electrolytic action with neg earth and you can fit modern accessories

bmcecosse wrote:It is exactly as described......cable from the non earth terminal of the battery - and spark it against the small terminal on the dynamo a few times.

Ok Thanks, I'll give it a go

mike.perry wrote:Go for the neg earth option, you get less electrolytic action with neg earth and you can fit modern accessories

So what are the advantages, if any ,to a positive earth system?

Nothing.......

Hi Folks, I fitted Jethro's new C40 dynamo this morning and after "flashing" it to the battery terminal as you advised it worked perfectly.
The ignition warning light went out as soon as the engine started and remained out even on tickover.
I took the opportunity to remove and flush the radiator and replace all the hoses and fan belt - the water pump seems fine so the new one that I have will serve as a spare. I will have a go at renovating the old dynamo and keep that as a reserve as well.
Thanks again guys for all your help and advice, it is really appreciated.

Dismantled the old dynamo and sure enough the brushes were stuck in their holders.
I will order a new set to be on the safe side as they looked pretty rough and pitted.

Great success!

[quote="bmcecosse"]Great success![/quote
With your help and advice, Much obliged.