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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / June 2005Why were so many British cars positive earth?
I did some Googling and came up with nothing. Hard to believe no one else has apparently ever asked this question. Or maybe I'm looking in the wrong place. Anybody know? (Besides "because they were British", that is...) So were a lot of old 6 volt American cars prior to about 1955. Mack > So were a lot of old 6 volt American cars prior to about 1955. > > Mack Interesting. And do you know WHY that was done? > I did some Googling and came up with nothing. Hard to believe no one > else has apparently ever asked this question. Or maybe I'm looking in > the wrong place. > > Anybody know? (Besides "because they were British", that is...) probably the same reason that Honda engines spin backwards. Because that's the way they did it? I'd like to know why the hot wire in car wiring is red and the ground wire is black, but at home it's the black wire that's hot. >> I did some Googling and came up with nothing. Hard to believe no one >> else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 7 lines] >I'd like to know why the hot wire in car wiring is red and the ground >wire is black, but at home it's the black wire that's hot. In house wiring the red wire is also "hot". >>> I did some Googling and came up with nothing. Hard to believe no one >>> else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 7 lines] >>I'd like to know why the hot wire in car wiring is red and the ground >>wire is black, but at home it's the black wire that's hot. >In house wiring the red wire is also "hot". Black is hot, IIRC. White is neutral. Red is only used for three plus ground as in wiring for a 3-way (three terminal actually) switch. >>>>I did some Googling and came up with nothing. Hard to believe no one >>>>else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 15 lines] > Red is only used for three plus ground as in wiring for a 3-way (three terminal > actually) switch. How do you figure one wire is hot while the other is neutral in AC wiring? > >>>>I did some Googling and came up with nothing. Hard to believe no one > >>>>else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 17 lines] > > How do you figure one wire is hot while the other is neutral in AC wiring? The neutral is bonded to ground in the distribution panel.  SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ "The beauty of a chainsaw is that you don't have to start it. Just show up with it." - Joe Walsh, on checking in to hotels >>>>>I did some Googling and came up with nothing. Hard to believe no one >>>>>else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 15 lines] >> Red is only used for three plus ground as in wiring for a 3-way (three terminal >> actually) switch. >How do you figure one wire is hot while the other is neutral in AC wiring? One is tied to a common point and at nearly zero voltage to ground (neutral). Also, the hot is the one that is switched. > >>> I did some Googling and came up with nothing. Hard to believe no one > >>> else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 15 lines] > Red is only used for three plus ground as in wiring for a 3-way (three terminal > actually) switch. Incorrect. Red is most certainly a "hot" lead in house wiring. For 240v circuits such as stoves, dryers, large A/C, etc. you have both black and red hot leads along with your ground and if needed a neutral. Also as someone else has noted, white wires can also be hot leads if the ends are marked with black or red tape. Pete C. > Incorrect. Red is most certainly a "hot" lead in house wiring. For 240v > circuits such as stoves, dryers, large A/C, etc. you have both black and [quoted text clipped - 4 lines] > > Pete C. I've never seen this. A 240V circuit uses the same (color) wire as a 120V circuit. And a neutral is not needed or wanted. > > Incorrect. Red is most certainly a "hot" lead in house wiring. For 240v > > circuits such as stoves, dryers, large A/C, etc. you have both black and [quoted text clipped - 7 lines] > I've never seen this. A 240V circuit uses the same (color) wire as a 120V > circuit. And a neutral is not needed or wanted. Sure it is, without a neutral you have no way of using one leg for a 120V circuit for, say, the light inside your dryer, or the timer motor for same... nate > > > Incorrect. Red is most certainly a "hot" lead in house wiring. For 240v > > > circuits such as stoves, dryers, large A/C, etc. you have both black and [quoted text clipped - 13 lines] > > nate You're right, I hadn't considered appliances. > > Incorrect. Red is most certainly a "hot" lead in house wiring. For 240v > > circuits such as stoves, dryers, large A/C, etc. you have both black and [quoted text clipped - 7 lines] > I've never seen this. A 240V circuit uses the same (color) wire as a 120V > circuit. And a neutral is not needed or wanted. > I've never seen this. A 240V circuit uses the same (color) wire as a 120V > circuit. And a neutral is not needed or wanted. European systems often do not use a 'neutral', but American designs may have to have it. I ran into this with an American clothes dryer in Norway which blew the breakers as soon as I plugged it it. I solved it by having a transformer wound to give me the 120-0-120 split. > > I've never seen this. A 240V circuit uses the same (color) wire as a 120V > > circuit. And a neutral is not needed or wanted. [quoted text clipped - 5 lines] > I plugged it it. I solved it by having a transformer wound to give me the > 120-0-120 split. Europeans do not use a 2 wire spilt phase 240V circuit as we do. That's why you had trouble. > > Incorrect. Red is most certainly a "hot" lead in house wiring. For 240v > > circuits such as stoves, dryers, large A/C, etc. you have both black and [quoted text clipped - 7 lines] > I've never seen this. A 240V circuit uses the same (color) wire as a 120V > circuit. And a neutral is not needed or wanted. Then apparently you haven't looked at any houses in the US since the days of knob and tube wiring. As for the neutral, for pure 240v devices a neutral is not needed however many 240v appliances also have 120v components and require the neutral as well. A 240v A/C unit usually doesn't need a neutral, a 240v electric stove often does need a neutral for things such as lights, convenience outlets, timers, etc. Pete C. >>I'd like to know why the hot wire in car wiring is red and the ground >>wire is black, but at home it's the black wire that's hot. > > In house wiring the red wire is also "hot". and the white wire can be hot too if it's got black tape on it. ;) My comment was just that it's "backwards" from cars and regular electronics - black is ground unless it's house wiring. I only do house wiring projects about once a year and I always have to remind myself of that... > >>I'd like to know why the hot wire in car wiring is red and the ground > >>wire is black, but at home it's the black wire that's hot. [quoted text clipped - 7 lines] > wiring projects about once a year and I always have to remind myself > of that... You haven't worked on German or Swedish cars. Brown is ground and black is hot. When trying to figure out which wire is hot don't assume that anything other than red color is not hot. It's a good way to get burned. > When trying to figure out which wire is hot don't assume that anything > other than red color is not hot. It's a good way to get burned. Wrong - Do not assume anything at all. Test everything when there is any question as to how things have been wired. In the US at least, red is very often a hot lead for a 240v circuit. Pete C. > > When trying to figure out which wire is hot don't assume that anything > > other than red color is not hot. It's a good way to get burned. > > Wrong - Do not assume anything at all. Test everything when there is any > question as to how things have been wired. In the US at least, red is > very often a hot lead for a 240v circuit. Without trying to get into an argument here, that was what I said. The original post said: My comment was just that it's "backwards" from cars and regular electronics - black is ground unless it's house wiring. I said in response to not assume that any color other than red is not hot. In otherwords everything is potentially hot. Or in yet other words, when you don't know the building or car, test everything. > Pete C. >>>When trying to figure out which wire is hot don't assume that anything >>>other than red color is not hot. It's a good way to get burned. [quoted text clipped - 16 lines] > >>Pete C. True, especially when you come across used cars that have all sorts of "unique" wiring... I've been guilty of using "what I had" instead of the right color... But any proper house wiring the black is hot and in most cars and electronics the "standard" for black is ground. (btw, this is Canada and the US only....) >I did some Googling and came up with nothing. Hard to believe no one > else has apparently ever asked this question. Or maybe I'm looking in > the wrong place. > > Anybody know? (Besides "because they were British", that is...) It actually makes more sense (to me) to have a positive ground since DC current flows from negative to positive. > >I did some Googling and came up with nothing. Hard to believe no one > > else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 4 lines] > It actually makes more sense (to me) to have a positive ground since DC > current flows from negative to positive. Well, it's a story with a long history. The Brits were on a roll when they declared Greenwich Mean Time as the time standard, so they also declared that cars (when developed) would always have a positive ground. Unfortunately the British Empire fell onto hard times and their advice was ultimately ignored and we now have Universal Coordinated Time and negative grounded cars. > > Anybody know? (Besides "because they were British", that is...) > > It actually makes more sense (to me) to have a positive ground since DC > current flows from negative to positive. No, actually it does not, John. DC flows from positive to negative, by convention. Electrons from from negative to positive, but electron flow is not defined as current. > > > Anybody know? (Besides "because they were British", that is...) > > [quoted text clipped - 5 lines] > Electrons from from negative to positive, but electron flow is not > defined as current. Back in my days as an electrical engineering student, we referred to positive current as the movement of "holes", and negative current as the movement of electrons. Of course everything has to do with the mass movement of electrons, but the convention of "positive current" never changed. Electrons and holes are also used to describe semiconductor doping. > > > > Anybody know? (Besides "because they were British", that is...) > > > [quoted text clipped - 13 lines] > > Electrons and holes are also used to describe semiconductor doping. This is all very interesting, to be sure. But nobody has answered my question of WHY? Was the positive-earth setup the result of a flawed understanding of electricity? Or was there some other reason to choose this layout? > This is all very interesting, to be sure. But nobody has answered my > question of WHY? > > Was the positive-earth setup the result of a flawed understanding of > electricity? Or was there some other reason to choose this layout? Because the British didn't know better. >>>>>Anybody know? (Besides "because they were British", that is...) >>>> [quoted text clipped - 19 lines] > Was the positive-earth setup the result of a flawed understanding of > electricity? Or was there some other reason to choose this layout? There's no flawed understanding of electricity. They probably just decided to go that way. There's no particular reason why a common grounding point has to be "positive" or "negative". There's no reason why we couldn't just switch everything such that "positive" current couldn't be switched towards the flow of electrons. These things were adopted by convention and haven't changed because most people prefer a "common language". >This is all very interesting, to be sure. But nobody has answered my >question of WHY? > >Was the positive-earth setup the result of a flawed understanding of >electricity? Or was there some other reason to choose this layout? Maybe not a "flawed understanding," but a change in theory about electricity. In school, studying automotive technology years ago, we were told that the change from positive to negative grounding had to do with electrical theory. I'm not enough of a physics major to make it perfectly clear, but it had to do with whether current flows from positive to negative, or from negative to positive. (And CURRENT flow is not necessarily defined as ELECTRON flow). Apparently there was a discovery or new understanding about the basic nature of electricity, some time just before most auto makers changed over from positive grounds to negative grounds. I don't remember enough detail, but there was thought to be an advantage to having it wired in a particular manner. Most U.S. vehicles were changed in the middle 1950s. The Brits came along about 5 years later. > >This is all very interesting, to be sure. But nobody has answered my > >question of WHY? [quoted text clipped - 17 lines] > Most U.S. vehicles were changed in the middle 1950s. The > Brits came along about 5 years later. It should make no difference to the operation of electrical equipment which polarity one chooses for ground. However, potential differences between two pieces of metal may result in corrosion of one or the other. By forcing one to a higher or lower potential, one can inhibit this effect. It is possible that positive grounds cause undesireable corrosion and reversing the polarity stopped or slowed it. Just a guess. SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ 2 + 2 = 5 for extremely large values of 2. > It should make no difference to the operation of electrical equipment > which polarity one chooses for ground. However, potential differences [quoted text clipped - 4 lines] > > Just a guess. Good guess.. corrosion is a problem in positive ground vehicles. Jim > Back in my days as an electrical engineering student, we referred to > positive current as the movement of "holes", and negative current as [quoted text clipped - 3 lines] > > Electrons and holes are also used to describe semiconductor doping. But holes only move in semiconductors, not normal wires. It is an even more useless argument than how many angels dance on the head of a pin. In a normal conductor the electrons do not actually "move" very far at all. Not even the free electrons. They move a little- the E field from that forces others to move, etc. It is like a bunch of balls sitting in a trough- one comes in, bangs stream of balls, one on end moves off, balls move about one diameter. Yeah, Es move a bit farther than their "diameter" but there is not really a stream of individual electrons moving down a wire and leaving the end like water in a pipe. > > Back in my days as an electrical engineering student, we referred to > > positive current as the movement of "holes", and negative current as [quoted text clipped - 15 lines] > individual electrons moving down a wire and leaving the end like water > in a pipe. It is true that the effect of electron movement is important rather than the distance an individual electron travels. The convention of current being defined as flow of positive charge, or its effect, has been there for a long time, long before hole movement was shown to be a reality. This is standard university physics (and chemistry). There are few cases where the actual direction makes much difference in practice. As another poster mentioned, corrosion can be induced by current, where there is an external electrolyte path. There are some snakeoil 'cathodic protection' devices sold by schlockmeister companies and they have been cited on this group. They are all but worthless for general automobile corrosion. In high school, my physics teacher dodged the positive ground question by saying that it was believed there were certain advantages. (He never said what they were supposed to be.) Maybe just the British tradition. Their practice of driving on the left at least had a reason. >> Back in my days as an electrical engineering student, we referred to >> positive current as the movement of "holes", and negative current as [quoted text clipped - 5 lines] > > But holes only move in semiconductors, not normal wires. In a pure sense, yes. But "holes" have been used as an abstraction to describe positive current in a conductor. I never said it was accurate. > It is an even more useless argument than how many angels dance on the > head of a pin. In a normal conductor the electrons do not actually [quoted text clipped - 5 lines] > individual electrons moving down a wire and leaving the end like water > in a pipe. Well - in a typical metal conductor there's really just a sea of free electrons. Push one in at one end and another pushes out at the other end. > > It actually makes more sense (to me) to have a positive > > ground since DC current flows from negative to positive. > No, actually it does not, John. DC flows from positive to > negative, by convention. Electrons from from negative to > positive, but electron flow is not defined as current. Just as Iraq had WMDs by Washington standards but not by reality. >>I did some Googling and came up with nothing. Hard to believe no one >> else has apparently ever asked this question. Or maybe I'm looking in >> the wrong place. >> >> Anybody know? (Besides "because they were British", that is...) >It actually makes more sense (to me) to have a positive ground since DC >current flows from negative to positive. DC flows in a circle. It makes absolutely no difference which side you use as your reference. >>>I did some Googling and came up with nothing. Hard to believe no one >>>else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 7 lines] > DC flows in a circle. It makes absolutely no difference which side you use > as your reference. Actually it does when you finally get to the coil. Other than that you're right there's not much difference. nate Signaturereplace "fly" with "com" to reply. http://home.comcast.net/~njnagel >> DC flows in a circle. It makes absolutely no difference which >> side you use as your reference. > >Actually it does when you finally get to the coil. Other than that >you're right there's not much difference. Not bad for a canned answer, but that's beside the points. Signature-john wide-open at throttle dot info > DC flows in a circle. It makes absolutely no difference which side you use > as your reference. Believe it or not, I bought a used Fiat 131 Mirafiore for my x-wife and upon one occasion the battery ran down for some unrelated reason. I took it out of the car to charge it, and something was very very wrong. The negative post on the battery was connected to the positive battery cable. No doubt about it. There was still enough voltage on the battery to measure and sure enough, the negative terminal was positive. Someone had charged it in reverse, and it had worked that way for a long time. I discharged the battery and recharged as God and Exide had intended, dealt with the unrelated problem, and started it up. Never had another problem. I would not have believed this was possible, but it did happen. > >I did some Googling and came up with nothing. Hard to believe no one > > else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 4 lines] > It actually makes more sense (to me) to have a positive ground since DC > current flows from negative to positive. Its a British car. Which way does the smoke travel? ;-) SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ I used to get high on life but lately I've built up a resistance. > > > I did some Googling and came up with nothing. Hard to believe no > > > one else has apparently ever asked this question. Or maybe I'm [quoted text clipped - 8 lines] > > ;-) Towards the Prince of Darkness... > Its a British car. Which way does the smoke travel? So you have read the smoke theory of electricity too! Dont remember where I saw it, but it relates, in an unusual way. > >I did some Googling and came up with nothing. Hard to believe no one > > else has apparently ever asked this question. Or maybe I'm looking in [quoted text clipped - 4 lines] > It actually makes more sense (to me) to have a positive ground since DC > current flows from negative to positive. I remember reading something decades ago that the reason for positive earth was spark plug electrode erosion. On the early spark plugs that is. Regards, Mik (the Brit ;) name the 1s you know 59-66 Sunbeam Alpine Series I-IV Bugeye Sprite Erich > name the 1s you know >Newsgroups: rec.autos.tech >59-66 Sunbeam Alpine Series I-IV >Bugeye Sprite >Erich >"TE Cheah" <no@spam.biz> wrote in message news:42bfa0f6_2@news.tm. >>net.my... name the 1s you know '52 MG TD MkII (in my garage) My recollection is that Chryslers in the '50's were positive ground too. Tom Willmon near Mountainair, (mid) New Mexico, USA Net-Tamer V 1.12.0 - Registered > name the 1s you know Most of them up to about 1960-'65. Many British cars with generators (dynamos) were positive earth. Even today, there are requests from classic owners on how to repolarise their dynamos to negative earth so as to be able to use modern radios and tachometers and such. As well, some owners want to be able to use their classics daily, in regular traffic. This usually means the need to convert the car to have negative earth and an alternator rather than a dynamo, necessitating the replacement of things like dashboard instruments. I gather (from the posts that were more-or-less on-topic) that the reason British cars were positive earth was the same reason American cars were positive earth: Convention and contemporary understanding of DC current. But only up to about 1950. Why they changed from positive to negative is alleged to have been 1) a change in the way DC current was understood, and 2) corrosion. I came across something interesting just today, however. <http://www3.usenetarchive.org/File.asp?service=24603> According to this reference, it had to do with...transistorised accessories. You know, to me this makes more sense than any other explanation I've yet come across. > Why they changed from positive to negative is alleged to have been 1) a > change in the way DC current was understood, and 2) corrosion. Yep. If there's one thing british "car" "engineers" were good at, it was finding ever more efficient ways of making a car rust. "Daniel J. Stern" <dastern@127.0.0.1> wrote in message > Yep. If there's one thing british "car" "engineers" were good at, it was > finding ever more efficient ways of making a car rust. They are good, but can't beat the Italians, Daniel. Hi, My father had a 1947 morris minor. I wanted to fix a radio which had a -ve grounded casing. All I did was reverse the battery connection and reverse the amp meter connection (so it shows +ve when charging). These old cars had no semi conductor devices and its dynamo is "not" fixed magnet. So just changing the battery polarity solved the problem! Harshana > > name the 1s you know > [quoted text clipped - 21 lines] > accessories. You know, to me this makes more sense than any other > explanation I've yet come across. > My father had a 1947 morris minor. I wanted to fix a radio which had a > -ve grounded casing. All I did was reverse the battery connection and > reverse the amp meter connection (so it shows +ve when charging). These > old cars had no semi conductor devices and its dynamo is "not" fixed > magnet. So just changing the battery polarity solved the problem! ...you're leaving out the part where you had to re-polarise the voltage regulator. > > My father had a 1947 morris minor. I wanted to fix a radio which had a > > -ve grounded casing. All I did was reverse the battery connection and [quoted text clipped - 4 lines] > ...you're leaving out the part where you had to re-polarise the voltage > regulator. Is there a permanent magnet in the regulator, or how else would that matter? My now severely dated experience with generator/dynamo regulators are with two, or three, coil Bosch units. I only remember that they sensed voltage and current, and I can't remember anything that would make them polarized. Thomas > > ...you're leaving out the part where you had to re-polarise the voltage > > regulator. > > Is there a permanent magnet in the regulator, or how else would that > matter? A generator regulator must be polarised or it will not work. Polarising the regulator is the last step in installing a new regulator, before firing up the engine and checking for charging. absolutely not. I did not re-polarise the voltage regulator. It had couple of relays in the regulator box, one picks-up when there is enough charging voltage and if I can remember right other picks-up when its over voltage, so the charging will happen through wire wound resistor. > > My father had a 1947 morris minor. I wanted to fix a radio which had a > > -ve grounded casing. All I did was reverse the battery connection and [quoted text clipped - 4 lines] > ...you're leaving out the part where you had to re-polarise the voltage > regulator.
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