1 reply to this topic

[Vince208]

Hi all,

I'm trying to convert my Mk1 mini from positive to negative earth. From what I've read it's really easy and I think I'm supposed to do just the following:

1. disconnect the small wire from the small terminal on the dynamo;
2. connect a jump wire from the large terminal on the dynamo (presumably with the large wire still connected) to the small terminal;
3. look for spark;
4. Re-connect small wire to the small terminal on dynamo.

The problem is, I don't get a spark. I assume that the battery has to be connected (or in my case a battery charger) and the ignition needs to be on, (both of which I have done)? I must be doing something wrong.

Also, what powers the spark? I can't get a reading on my voltmenter from either dynamo wire to earth. Surely there should be a voltage on one of these wires (presumably the larger one as the smaller one is apparently to be disconnected and not touched, although this appears counter-intuitive to me) when the ignition is on? All the other electrics work and the dynamo charged fine when connected as positive earth. I have not started the car for a couple of years.

Could I have introduced a problem by inadvertently connecting the small wire (rather than the small terminal) to the large terminal? Surely not if there's no voltage? Surely I couldn't have introduced a problem in the black regulator box on the wing or damaged the dynamo? The instructions on the internet don't give any warnings of things to be aware of / potential problems.

The coil got very hot but I assume this is un-connected and was just because I had the ignition on for about 15 minutes and the points may have been at their open state.

Any help will be much appreciated. Thanks. I won't be content until I witness that spark.

[crispdust]

I've swapped another car round to negative earth before, (not a mini though) but it was a lot more involved.

The battery terminals need to be swapped over, otherwise the body would still be positive? The dynamo needs swapping round, I can also imagine the voltage regulator would need changing as well. On the one I worked on we had the dynamo, and voltage regulator donated with wires attached so that was easy. It was also mechanical fuel pump. I'm not sure if the change in polarity would affect the operation of an electric fuel pump.

Finally you'll only see a spark if the points are opening and closing.

Sorry i can't give you a complete rundown, but I thought I'd let you know it's not that easy. I do know, that some of the guages didn't take to the negative earth, and Before I got a chance to check them my mate connected everything up while I wasn't there to surprise me the next morning. I was surprised at how the fuel guage, and water temp had fried!

Dan.