Positive ground electrical systems?

[Franco Cozzo]

Hey guys, just curious if anyone knows the reason for older cars, particularily British ones for using positive ground electrical systems back in the day? Why be the opposite to everything else?

Was there a particular reason?

[2011G6E]

Kind of makes sense...anywhere you stick a wire onto the car, it's going to be live.
The earthing issues are a nightmare though..

Neither of my English cars had it...a 1973 Austin A30 and a 1957 Morris Minor...but I heard from other guys with positive ground cars that it was a pain in the ****...

[mik]

yes i can remember as a young buk doing the jump start on my mini, and touched doors while the jumpers where connected, got quite a nice spark off it, agreed pain in the kyber. have no idea the reason for + earth system.

[Yellow_Festiva]

My 59 Sprite left the factory like that. As for why? No idea. I actually can't remember if it was converted to neg earth now that I think of it? It ran 12v electrics but still used a generator. Sold her several years ago ;(

[GTP534]

My first car was a 66 Ford Cortina 440. It had a positive earth system. I remember Tandy had a warehouse sale and I bought this auto reverse cassette player (wow!) to fit under the dash. My dad was an electrical engineer and of course he wanted to check the earthing before installing it. He solved the problem by isolating the mounting screws from the dash and wrapped the mounting bracket in tape. Worked a treat!

[Bushbasher]

A lot of Mitsubishis' are positive ground, I know my Delica is, it's bluddy annoying.

[cs123]

The switch to negative earthing was more of a standards thing IMO.

The only reason I can think of where positive earth is superior is to protect from galvanic corrosion and this may have been a reason why car electrical systems started off being positive earthed. Old telephone exchanges use DC (50v) power and they are positive earth, for this reason I believe.

[aussiblue]

Most cars (UK and US and Oz) were positive earth at one time and it was the introduction of car radios that motivated the change to negative earth as positive earth vehicles caused more interference to the radios (or it was more difficult to achieve effective suppression). The UK lagged behind the 1940's change as unlike the affluent post war US in the UK car radios were very much a rare luxury item.

[LTDHO]

Dad's Zephyr is pos ground, only pain was wiring the new HU.

[last fairlane]

Dont worry about pommy cars
the mighty Mack coolpower back in the seventies was positive earth
I know I killed a almost brand new Sony radio cassette
and any one that was around then they were about
half a weeks wages to buy
and you swapped them from car to car
those were the days

[Olbucko]

Originally Posted by GTP534

My first car was a 66 Ford Cortina 440. It had a positive earth system. I remember Tandy had a warehouse sale and I bought this auto reverse cassette player (wow!) to fit under the dash. My dad was an electrical engineer and of course he wanted to check the earthing before installing it. He solved the problem by isolating the mounting screws from the dash and wrapped the mounting bracket in tape. Worked a treat!

A friend of mine had a Cortina in the midd 60's with pos earth, it took about one min to convert it to neg earth, he connected the battery around the other way then held down the contacts in the voltage regulator for about a second, simple as that. I think that changed the polarity of the generator, that's all that mattered. The starter still turned in the same direction because of the way it was connected internally. Any old auto elctrician over 60 would know how to do it.

[FGII-XR6]

just the sameas why some cars are left or right hand drive some countries originally decided positive earth was the way to go. the only real difference is when you install equipment which is polarised like a radio . the one thing they did find though is positive earth cars tend to rust more.
in old positive earth cars they could be changed over by changing the alternator and starter and reversing the battery terminals . also any other polarised equipment needs changing but in older cars this is not a big problem as would only be an old AM radio. as far as the alternator ( or more likely generator) and started are concerned if the right one is not available an auto electrician would be able to convert them with some internal rewiring

[dave351cid]

Originally Posted by au3xr6

. the one thing they did find though is positive earth cars tend to rust more.

thats what what i was told as well. an old mechanic / auto electrician told me that most of the old cars were originaly positive earthed and the main reason that the standard was changed to negative earthing was to combat the rust problem. this story was also backed up by a metal corossion scientist.

this topic also relates to the other thread thats talking about the effectivnes of electronic rust prevention systems.

[zilo]

I cannot see how earthing a car one way or another can determine the rust vulnerability factor.

The vehicles electrical system is independent of the earth by being on rubber tyres, excellent insulation.

In any event there is no current flow from the car to earth.

The most likely reason that a negative earth standard was adopted was the electronics industry settling on negative grounds for equipment such as radios, tape players, fans, lighting etc.

The transistors predominantly used still to this day, are based on silicon rather than earlier germanium based ones and typically would have the emmitter polarity at negative potential in relation to the power source.

Seems fair enough to me.

[cs123]

Originally Posted by Ugg

In any event there is no current flow from the car to earth.

For cars the chassis = earth.

[FGII-XR6]

nothing to do with returning to actual earth it is due to electrolisys, the positive earth system encourages rust due to electrolosys

Originally Posted by Ugg

I cannot see how earthing a car one way or another can determine the rust vulnerability factor.

The vehicles electrical system is independent of the earth by being on rubber tyres, excellent insulation.

In any event there is no current flow from the car to earth.

The most likely reason that a negative earth standard was adopted was the electronics industry settling on negative grounds for equipment such as radios, tape players, fans, lighting etc.

The transistors predominantly used still to this day, are based on silicon rather than earlier germanium based ones and typically would have the emmitter polarity at negative potential in relation to the power source.

Seems fair enough to me.

[Sprint]

yeah a electrical/chemical reaction due to ion changes in the molecular structure of metal changing it basically back to dirt or ore lol.

as you explained electrolosys.

Rust is hard to beat,your fighting nature.

the are some electronic products that stop the reaction happening on metal or i should say help slow it down.

Even today in electronics there is still a oposite current theory and its american haha.

It works on the princible of current flowing from neg to posative, exactly opposite to what 75% of the earth now study.

I think this goes back to newton vs bell(the other guy?) and DC current vs AC

It's rather the beta tapes system of electronics thinking but its still current thinking in some parts of the world.

[Sprint]

Most bridges ,buildings and metal frame objects have electronic help.

Sydney harbour would.

[aussiblue]

newton vs bell(the other guy?) and DC current vs AC

I think perhaps you mean George Westinghouse versus Thomas Edison with Nikola Tesla as a minor combatant.


See http://en.wikipedia.org/wiki/War_of_Currents

Newton and Bell were not even contemporaries with Isaac Newton (the man famous for gravitational theory) dying in 1727and Alexander Graham Bell (famous for the telephone) not being born until 1847.

[aussiblue]

Most bridges ,buildings and metal frame objects have electronic help.

Cathodic protection using a sacrificial anode is usually used for metal object immersed in water or containing water (e.g. bridges, jetties, boats, storage hot water systems). The lack of a conductive medium coating the metal surface (i.e water) makes it difficult to use with cars and similar dry objects.

Another less often used and more difficult to manage option is anodic protection (see http://www.westcoastcorrosion.com/Pa...20&%20Apps.pdf) which is usually used in very acidic environments (mild or stainless steel equipment use for concentrated sulphuric acid, paper mill digesters and recausticizing storage tanks). In theory if all the metal in the car was coated with a suitable medium cathodic or anodic protection would work for a car but I (and the ACCC as I recall) am very skeptical of the most of the electronic products that are sold to protect cars from corrosion.

The practical difficultly with electronic protection is that unless there is some means of monitoring and automatically adjusting the current density or potential to ensure you are getting the anodic or cathodic state you desire it might make things worse rather than better. There is also the difficulty of ensuring the current flows through all the parts you want to protect and some who sell these devices also package it with a conductive coating that is sprayed on (but then why not simply just spray the whole car with with probably cheaper and more effective deodorised fish oil?).

Also see http://www.siliconchip.com.au/cms/A_100606/article.html although they also seemed to have forgotten about the lesser known option of anodic protection.

Also see: http://www.automotivehelper.com/topic219494.htm


Quote:
"There have been two very good papers presented on the lack of scientific basis for using CP in this application:


Baboian, R., CATHODIC PROTECTION OF AUTOMOBILES, DOES IT WORK, NACE
Paper, Corrosion/87, 1987 and Materials Performance, Vol. 26,
no. 7, 1987.


Baboian, R., STATE OF THE ART IN AUTOMOBILE CATHODIC PROTECTION, PROCEEDINGS OF THE 5TH AUTOMOTIVE CORROSION AND PREVENTION CONFERENCE, SAE p-250, Society of Automotive Engineers, 1991 and SAE Transactions, Sept, 1992.


The [US] Federal Trade Commission has taken a firm stance against firms that make claims of protecting cars by this technique."
http://www.ftc.gov/opa/1995/08/rustevad.shtm

Quote: "The Federal Trade Commission has charged RustEvader Corporation, the marketer of a purported electronic corrosion-control product for automobiles that is sold under the names "Rust Evader," "Rust Buster," "Electro-Image," and "Eco-Guard," with making false claims about the product, as well as about a demonstration and studies regarding its efficacy. The FTC also alleged that Rust Evader illegally included in its warranty a provision that requires consumers to pay for a bi-annual inspection at an authorized RustEvader dealer to keep their warranty in force."



also see:
http://www.corrosion-doctors.org/Car...c-car-rust.htm
http://www.dansdata.com/danletters153.htm

Off course if you chose to park your car in swimming pool, as some errant drivers have, Cathodic protection might be useful.

[Sprint]

ahh yes a metal made to conduct corrosion before the object needed to protect.yeah ive seen that on documentries.

thanks for the corrction's aussiblue.

I could not think of the names thats why i had the ?, but i do know it was a war between AC and DC, reverse polarity.

of course newton the physics lol.

had the wrong names but right idea.

[aussiblue]

"Now if the battery hasn't shorted, I know my electronic rustbuster is working."

[aussiblue]

and rather than preventing rust they can cause car fires:

http://www.recalls.gov.au/content/in...itemId/1013516

[Streets]

Originally Posted by aussiblue

I think perhaps you mean George Westinghouse versus Thomas Edison with Nikola Tesla as a minor combatant.


See http://en.wikipedia.org/wiki/War_of_Currents

I expected to see pictures of three men in primitive copper power-suits shooting electricity out of their hands at each other and instead I get this

[whales]

My Anglia had + earth but i converted it to - earth so it was easier to wire in tachos and radios etc. From memory all that had to be done was to swap battery leads, coil wires and self excite the generator to accept the other polarity.

[XD 351 Ute]

I was positively earthed once, got my finger between the earthing strip & the spark plug on a Briggs & Stratton powered cement mixer.

Certainly livened me up for the day..

Ed

[devilcv8]

Originally Posted by cs123

Old telephone exchanges use DC (50v) power and they are positive earth, for this reason I believe.

Not just old, even today they are still positive earthed and 54v DC or 52.8vDC.

What gets fun is HOD and LOD power distribution.


Ex telco tech.

[Olbucko]

Originally Posted by whales

My Anglia had + earth but i converted it to - earth so it was easier to wire in tachos and radios etc. From memory all that had to be done was to swap battery leads, coil wires and self excite the generator to accept the other polarity.

That confirms what I said in my earlier post, a one minute job to changeover from pos to neg earth. Can only be done if the car has a generator. If the car had an alternator you would have to change it (and the regulator) for one that was suitable for use in a neg earth system

[Franco Cozzo]

Originally Posted by Sprint

yeah a electrical/chemical reaction due to ion changes in the molecular structure of metal changing it basically back to dirt or ore lol.

as you explained electrolosys.

Rust is hard to beat,your fighting nature.

the are some electronic products that stop the reaction happening on metal or i should say help slow it down.

Even today in electronics there is still a oposite current theory and its american haha.

It works on the princible of current flowing from neg to posative, exactly opposite to what 75% of the earth now study.

I think this goes back to newton vs bell(the other guy?) and DC current vs AC

It's rather the beta tapes system of electronics thinking but its still current thinking in some parts of the world.

We've been taught at school current flows from negative terminal to the positive terminal, not the other way around.

[excopau]

cathodic protection on gas pipes using impressed current or scarificed anodes of different material to drive current flow and the anodes wear away while protecting the metal you wanan protect.