Tony B Posted April 2, 2012 Share Posted April 2, 2012 Could some one make sure I've got it right? If the wire from the ignition switch goes to the - side of the coil, the vehicle is a positive earth. Quote Link to comment Share on other sites More sharing options...
ajmac Posted April 2, 2012 Share Posted April 2, 2012 Thats correct -ve to ignition is +ve earth. Quote Link to comment Share on other sites More sharing options...
Tony B Posted April 2, 2012 Author Share Posted April 2, 2012 Thanks. Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted April 2, 2012 Share Posted April 2, 2012 Unless someone put the coil on the wrong way round :cool2: Quote Link to comment Share on other sites More sharing options...
Tony B Posted April 2, 2012 Author Share Posted April 2, 2012 Unless someone put the coil on the wrong way round :cool2: Make my day why don't you? :-D I know she runs, so check at least twice, then change coil. Quote Link to comment Share on other sites More sharing options...
RattlesnakeBob Posted April 2, 2012 Share Posted April 2, 2012 regarding this question... .........why do various manufacturers use different earths???. why don't they all make all vehicles negative earth ??? ..what is the advantage with either of the different pole earthings ? .............................is there any difference or advantage???:undecided: Quote Link to comment Share on other sites More sharing options...
Tony B Posted April 2, 2012 Author Share Posted April 2, 2012 I've been told that Positive earth is less likley to cause corrosion build up on the battery. But can cause electrolosis on the chassis. An Anode ie positive is more likley to be effected by corrosion. Quote Link to comment Share on other sites More sharing options...
Pete Ashby Posted April 2, 2012 Share Posted April 2, 2012 regarding this question............why do various manufacturers use different earths???. why don't they all make all vehicles negative earth ??? ..what is the advantage with either of the different pole earthings ? .............................is there any difference or advantage???:undecided: You may well remember that BMC later to become British Leyland had a love affair with +ve earth for about 20 years only to drop it and go back to conventional -ve earth systems. I have seen all sorts of explanations as to why the world should adopt +ve earth as standard but none seem to have stood the test of time. Trying to coax positive earth mini's to start on cold damp days was just as difficult as -ve systems. Pete Quote Link to comment Share on other sites More sharing options...
Lauren Child Posted April 2, 2012 Share Posted April 2, 2012 (edited) I may be going mad here but why does the coil have + and -. Surely a coil of wire doesn't have a polarity and will work either way around? The ignition could be on either side and make or break the circuit. Edited April 2, 2012 by Lauren Child Quote Link to comment Share on other sites More sharing options...
fv1609 Posted April 2, 2012 Share Posted April 2, 2012 I may be going mad here but why does the coil have + and -. Surely a coil of wire doesn't have a polarity and will work either way around? That is true but the way the coil is polarised will determine the polarity of the spark. I know a spark is a spark & will ignite the petrol vapour but the ideal arrangement is when the centre electrode is negative. In that arrangement a spark is more effective when launched from the hot centre electrode to the relatively cold earth terminal rather than the other way around. Having -ve earth or +ve earth coils is merely to establish the correct way of operation to ensure what one might call a "negative spark". (Best not to think too much about these things as electrons flow in the opposite to charge & it can get a bit befuddling) Quote Link to comment Share on other sites More sharing options...
Lauren Child Posted April 2, 2012 Share Posted April 2, 2012 That is true but the way the coil is polarised will determine the polarity of the spark. I know a spark is a spark & will ignite the petrol vapour but the ideal arrangement is when the centre electrode is negative. In that arrangement a spark is more effective when launched from the hot centre electrode to the relatively cold earth terminal rather than the other way around. Having -ve earth or +ve earth coils is merely to establish the correct way of operation to ensure what one might call a "negative spark". (Best not to think too much about these things as electrons flow in the opposite to charge & it can get a bit befuddling) Thanks Clive :tup:: Quote Link to comment Share on other sites More sharing options...
Tony B Posted April 3, 2012 Author Share Posted April 3, 2012 (edited) Go on Clive. Let's throw in conventional and electron flow, just for fun. So to boil the answer down, as long as the Bu**er starts and gets me to where I want to go who cares? Though I have got an electronic ignition to fit, at that point it does matter. The coil acts as a transformer. The opening and shutting of the points causes an oscolating magnet feild so allows the coil to boost the voltage. The higher voltage allows the current to jump the air gap on the plugs, this creates the spark. The same sort of system also creates radio waves, hence the sheilding needed particullaly in FFR vehicles. The heat bit is because a Cathode, ie Negative polarised plate will excite electrons when it is warm, so they will jump to an Anode or positve plate. That's why the old thermionic valves had a heater in the valve and sets had to litterally 'Warm Up'. Electrons being a negativley charged particale will flow to a positive Anode. Unlike charges attract. That is Electron flow. In practice it dosen't matter to much, which is why most people work on a current going from positive to negative, conventional flow. Edited April 3, 2012 by Tony B Quote Link to comment Share on other sites More sharing options...
fv1609 Posted April 3, 2012 Share Posted April 3, 2012 Best not to think too much about these things :-D:-D Quote Link to comment Share on other sites More sharing options...
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