Positive Earth Charging System

[GatorZilla]

Hey Y'all! I need help again!

My Precious has a positive earth system...

I got my new dynamo in the mail today and it says "negative earth"

HELP!

What do I need to do?

Do I re-do it and make Precious have a negative earth system or what?

I know my husband would probably know what to do, but I am trying to get my head wrapped around the problem and try to see what needs to be done. I figured all y'all's cars would most likely still have a positive earth system, too.

Any advice would be greatly appreciated!

Thanks a bunch!

[Fingolfin]

I'll be cautious and say it depends on the dynamo, but dynamos are tough things (tougher than alternators anyhow) and any dynamo can probably be "shocked" into the opposite polarity. The way one does this is, leave the dynamo disconnected from the car, and take a long lead from the live side of the battery (in your case, the negative terminal) and touch the lead for five to ten seconds to the small terminal on the dynamo (if the dynamo is a standard Lucas thing). I think I've got that right.

Alternatively, changing over the car to negative ground is really easy. Your decision. But I would think any dynamo, once its magnetic memory has been wiped (and, come to think of it, why should a brand-new dynamo have any magnetic memory anyway?), would be able to supply power with either polarity.

[Trickydicky]

Here is a guide, http://www.mmoc.org.uk/index.php?page=322.

[bmcecosse]

Don't hold the lead on for '5 to 10 seconds' - it just needs a quick 'flash' against the small terminal - do it a couple of times just to be sure to be sure.

[GatorZilla]

Thank y'all SO MUCH!!!!!!!!

Turns out my husband knew what to do, but even I could do it now after your ever-so-kind-and-informative responses! I am just really wanting to learn everything that I possibly can about Precious so that if anything starts to go wrong, I MIGHT stand a chance of helping her, rather than hurting her.

I am still undecided about changing the system from positive earth to negative earth... I really want to keep her as original as I can, but the sad truth is, if something happened and I needed to get my battery "jumped off" it would fry the brain of the car that was helping me out as it is now...if I switch it over to negative earth then I could get help without fear of damaging the other vehicle...

Keith says that she belongs to me so it is my decision to make, but I am really having a hard time with this....

Decisions, decisions! Grrrrr!!!!!!

[bmcecosse]

TBH - as long as you don't want to fit a wireless or a Satnav - or charge up a Smart phone etc - I would leave it as it is. Anyone 'jumping' it just needs to observe the polarity - there is no risk as long as they do that - and the two cars are not touching of course.

[Fingolfin]

Roy, I said "five or ten seconds" because that's what Rob says in his guide. To wit: "Disconnect both dynamo leads and use a long length of wire to connect the small dynamo terminal to the battery positive [when changing to negative ground] for five to ten seconds."

As to jumping, just carry around a starting handle!

[bmcecosse]

I have no idea who 'Rob' is....5 to 10 seconds is far too long - a 'flash' is all it needs. I've done it many times in the past.. Anything else could lead to overheating of the wire = burned fingers!!

[Fingolfin]

It really makes no difference, but I was talking about Rob Thomasson, the author of the negative earth guide that was earlier mentioned. In that guide he's listed as "MMOC Technical Advisor." Linked again for full transparency...http://www.mmoc.org.uk/index.php?page=322

[katy]

Roy's correct,

a 'flash' is all it needs

[Fingolfin]

Okay. I was just conveying information I'd seen! No argument from me.