13 replies to this topic

[mini=love]

Ok well i have a 1972 mini that has a dynamo, and regulator box on the inner wing.

Now my quesion is how do i know if it is still positive earth or if it has been converted to negative earth?

I have tried to search but i cant bring much up all i can find is that i need to change the polarity, but how do i do this and he do i know if it has already been done before?

[danrock101]

The earth strap will go to the negative terminal on the battery if it's negative earth

Edited by danrock101, 11 October 2010 - 07:43 PM.

[mini=love]

Yes i know that but there is not battery fitted, thats why im asking...

As originally the car was positive earth, but it is a common thing to change them to negative earth, but i dont know if this has been done.

Edited by mini=love, 11 October 2010 - 07:51 PM.

[mk1leg]

I think yours would be Pos+ earth unless someone has repolorised the reg box ...doed it have a radio this will tell you wich way its earthed..............

[danrock101]

Yes i know that but there is not battery fitted, thats why im asking...

As originally the car was positive earth, but it is a common thing to change them to negative earth, but i dont know if this has been done.

haha, I did get a little worried and tried to answer without taking the ****

[dklawson]

1972 positive earth? Really? I thought the transition was earlier than that.

Regardless, the battery post/terminals are different sizes with the positive terminal being larger in diameter than the negative one.

If you measure the inside diameter of the cable clamps in the boot, the one with the larger hole will be for the positive battery terminal. Once you know which is larger you just need to look at where it is connected (boot floor... or cable going to the front of the car).

[mini=love]

Thanks for the replies, yep 1972 is positive earth originally well atleast mine was, it still has the sticker on the rocker cover.

It doesnt have a tape player fitter or any wiring for a tap player, so unfortunately i cant check that way.

Do you know how i check the regulator box to see if it has been repolorised?

I have fitted the battery, and the terminals fitted with negative earth, i presume this is correct then as the terminals fitted, if if there is a way i can check i really would like to so i can know 100% that it is right.

[Spitz]

Thanks for the replies, yep 1972 is positive earth originally well atleast mine was, it still has the sticker on the rocker cover.

It doesnt have a tape player fitter or any wiring for a tap player, so unfortunately i cant check that way.

Do you know how i check the regulator box to see if it has been repolorised?

I have fitted the battery, and the terminals fitted with negative earth, i presume this is correct then as the terminals fitted, if if there is a way i can check i really would like to so i can know 100% that it is right.

I had thought all MkIII MINIs were negative earth.
Your valve cover and or engine could very well be from another car....one that was fitted with dynamo, hence the regulator as well.

[mini=love]

Thanks for the replies, yep 1972 is positive earth originally well atleast mine was, it still has the sticker on the rocker cover.

It doesnt have a tape player fitter or any wiring for a tap player, so unfortunately i cant check that way.

Do you know how i check the regulator box to see if it has been repolorised?

I have fitted the battery, and the terminals fitted with negative earth, i presume this is correct then as the terminals fitted, if if there is a way i can check i really would like to so i can know 100% that it is right.

I had thought all MkIII MINIs were negative earth.
Your valve cover and or engine could very well be from another car....one that was fitted with dynamo, hence the regulator as well.

Hmm thanks for the reply, would be a very starnge thing to do as the wiring loom is completely standard, and uncut, so would have had to change the complete loom at the same time...

Just doesnt make sense to me why you would go through all that work when you could have just kept the original alternator.

The engin no is 99h353E-H317492

[dklawson]

In response to the control box question, it is really the field coils of the generator/dynamo that are polarized, not the control box.

Since there is no battery installed and no real electronics to deal with, this is a very, very good time to consider converting to negative earth. There are many articles online for how to do this and they are more complete than trying to remember all the steps and post them here. I suggest a visit to MiniMania.com. Check out their technical articles and read over the one or two they have on changing polarity. Read them through a couple of times and then post your questions here. The conversion isn't difficult but you do need sort of a checklist to make sure you've done everything.

[mini=love]

Thanks for the reply dklawson. I just tried the battery the other way round and the terminals dont fit, so i guess it has been converted at some point, but i really would like to make sure anything else that would have needed to be changed has been.

I have tried to search on minimania.com, but i cant find any information on what needs to be done to convert to negative earth wile keeping the dynamo. I have found a thread about converting to alternator and that says that i need to change the battery terminals round and swap the terminals round on the coil.

Edited by mini=love, 12 October 2010 - 03:05 PM.

[ado15]

Connect your battery with the negative terminal going to earth.

Remove the two leads from the dynamo.

Connect a short lead between the two terminals and a longer lead to one of the terminals.

At the starter solenoid, touch the other end of the longer lead to the large battery feed terminal (opposite terminal to the starter lead attachment) several times. It'll spark a little, but don't worry.

The dynamo will now be correctly polarised.

Remove the two temporary leads and reconnect the original wiring.

HTH.

Edited by ado15, 12 October 2010 - 03:04 PM.

[dklawson]

Try this article on polarity conversion:
http://www.minimania...fm?DisplayID=81

[mini=love]

Perfect expains everything very clearly there.