Bugeye grounding 101

[ichthos]

OK, I need a lesson on batteries. In general, does it make a difference if a car is positivley or negatively grounded? What are the advantages/disadvantages to either set up? There was no battery in my car when I bought it, consequently I am unsure of a number of things. Were all BE's positively grounded? Mine is a 1960. Is the battery different with a positive ground - does the positve terminal need to be closer to the body? Any help would greatly be appreciated.
Kevin

 

[drooartz]

Bugeyes were all positive ground from the factory. Doesn't really matter where the terminals go, so long as your cables all fit.

<span style="font-style: italic">Edit:</span> For clarity, I mean that it doesn't matter if the terminals are close to or far from the firewall... it definitely makes a difference if you do positive or negative ground.

 

[Dug]

Hold on, it does matter; there are things that need to be watched and changed. On another site (Minimania) they have information on changing polarity. Most likely here as well but I'm unaware of location.
Thankfully the MKI’s do not have an electric tack so that’s one item eliminated. Sure "some" folks have been lucky in the past, but in the words of dirty Harry…do you feel lucky______! Lots to consider.
dug

www.minimania.com/web/SCatagory/ELE...chnical Information/DisplayID/81/ArticleV.cfm

 

[ichthos]

So, this was originally positive ground. How can I tell how it is grounded now, since I have no idea what the PO did before me? Should I just hook it up with a positive ground and see what happens? What will happen if I am wrong? If there had at least been a battery in there, I would know how it was grounded. What else can I check to see if it is set up with positive or negative ground?

 

[Golden_Swan]

To see how it <span style="text-decoration: underline"><span style="font-style: italic">was</span></span> set up, if you have the old battery cables, the positive terminal is slightly bigger than the negative terminal.
Otherwise, negative ground works better, that's why all car manufacturers have gone that route. Don't ask me for technicals on that, some others here, like our resident electrical genius Sarastro, could give you the reason. I'm not that much up on electrical theory.
Plus you can get many more cool things for negative ground cars.

 

[spritenut]

Check the coil wiring. If terminal SW (or +) has the solid white wire to it, it is positive ground.
If CB (or -) has the solid white wire, it is neg ground.
On a Bugeye, that is the only thing that needs to be switched besides repolarizing the generator.
And only 1 time I had my heater blower motor run backwards after a + to - grd swap. That is simply a matter of switching the wires at the blower motor if it sucks air out of the cockpit.
Also if it's not a concours restoration, get a battery with the terminals AWAY from the firewall according to how your car is grounded.
Many if not all Spridgets have rusted out spots from battery gas because the terminals are too close to the metal firewall.
The battery is group 24, and the reverse terminal location is a 24F

 

[bugimike]

One thing other than the coil wires that I had to reverse to switch polarities is the wiring to the fuel guage which will read full when empty and empty when full if a Pos. Grnd. car is switched to neg. Another thing you could check is cable from the ground on the body (down by the starter on a BE) black (-) or red (+)? (This may offer a clue but is not conclusive as a DPO could have replaced it with one that is the right length but wrong color!).

 

[ichthos]

I forgot to say that currently there is no wiring harness in my car or wiring period. Maybe I am making this too difficult. I like to keep things stock, mainly because I can read a book later or ask someone for help later to figure out what to do if something goes wrong. After reading feedback on the forum concerning my wiring harness, I am going to put in a new wiring harness. If I hook everything like it was originally, I should be fine, right? I still don't understand why it makes a difference if it is positive or negative ground. My elementary understanding of electricity is that the positive or negative just denotes where the electrons exit and enter. I don't see what difference it makes what direction it goes. I know there must be more to it, but so far no one can tell me why negative grounding is better.

 

[jlaird]

Positive or neg, ground makes no difference. The only thing is to spark the generator for which ever. i can provide instructions if you need. no prob.

 

[ichthos]

Thanks for all the suggestions and offers for help. I think I am going to see what I can sell on EBay to get some money for the wiring harness....I'll be back.
Kevin

 

[bugimike]

The only reason that neg. ground would be better is that it falls in line with the way most cars are wired. If you would ever need a jump start, with a pos. ground car you would be out of luck! Another benefit with neg. ground is the availability of accessories such as a radio/stereo system that would not be compatible with pos. ground!

 

[jvandyke]

Stupid question maybe, but can't you go right off the neg/pos terminal of the jumper battery to corresponding terminals of the other?
I've got a negative ground stereo in my (as of yet) positive ground midget. It's wired straight to the battery and as long as I don't ground the chassis of the stereo anywhere I'm alright. Ideal? no, safe? no, alright for a little while? Yep.

 

[Bruce_B]

Yes you can.. If another car jumps you, just make sure the bumpers of the
car aren't touching, and then as with any other car, attach (+) to (+) and
then (-) to (-).

There is one difference, do not take the cable from his (-) to your car body/block etc. Some people ground that cable to the car, rather than the battery terminal for safety.

You're also right with your radio. As long as it doesn't touch any metal/ground of your car, you're OK.

 

[Sarastro]

That's right, but my greater worry with jumping a positive-ground car is that the person doing it might not notice it's positive ground, connect the negative to the chassis, the positive to the ungrounded battery terminal, and ka-POW! I'll bet most young road-service guys don't even know that some cars, in the past, were positive-ground.

Beyond that, it probably doesn't matter what you use until you start adding electronics. Then, I'd make sure it's negative ground. Even if you find, say, a positive-ground radio, you might not find a positive-ground version of the next electronic item you want to add. Then you'd have to do the conversion anyway and discard the original positive-ground radio.

So, this is a good time to do the change. Just assume it was positive ground and go through the process for converting it. I can't find my link to instructions for this, but do a search in the archives or google it and you'll find plenty of info. The main things are "flashing" the generator's field coil (it's not what you're thinking!), reverse the ignition coil's low-voltage terminals (you probably won't notice the difference if you forget this), and maybe reverse the connections to the fuel gauge--I'm not sure about that, but if it reads backwards, reverse it. I think that's it--but don't trust my memory, if you know what's good for you. Find some hard info.

Most important is probably flashing the generator. This is just connecting a wire briefly (like a couple seconds) from the battery + terminal to the generator's field coil terminal, before connecting up the generator. This sets the residual magnetization of the field to be correct so that the generator generates the right polarity when it starts up. I'm not sure what will happen if you forget this, and I don't want to know--either nothing, or something not very pretty. I wouldn't take the chance.