Conference terri::cars_uk

    Dick, 
    
    Let me get back to my Old Man before replying: He used to be a
    "scrappie" and knows all these old thinys . I'll get back to you.
    
    Cheers,
    
    	Les
    
    
    

>>    Connect battery minus to chassis and battery plus to F terminal on
>>    dynamo for a few seconds.
    
    I thought the process involved 'stroking' the dynamo with the lead.
    Dunno where I heard that though, I'm sure someone knows the truth...
    
    J.R.

    
    There was an old wive's tale that went 'changing the polarity of a car
    resulted in problems with rust later'. 
    
    Anyway why change it? If your fitting an accessory with the wrong
    polarity then insulate it and run two wires to it.
    
    
    Bill

    It's known as 'flashing the field' - a dynamo needs residual magnetism
    in the field to enable it to 'bootstrap' itself when starting from
    stationary. .0 got it right - just touch the battery +ve lead to the F
    terminal on the dynamo and it's converted - you get a good 'flash' due
    to the high inductance of the field winding.
    
    One thing I am not certain about is if you need to do something similar
    to your electro-mechanical cutout/regulator?
    
    - John.

    
       Don't sue me but I'm converting the Electron by the same technique as
    .0 plus polarising the dynamo as mentioned. Don't think you need to
    touch the control box.
    
       The problems associated with rust were the reason behind converting
    from +ve to -ve.
    
       Do you want me to go first and post the results ??!!
    
                                                          Chris.
    
    

    Re the ``Old wives tale''.
    
    	A postive earth car will rust LESS than the current -ve earth cars.
    

    
    From what I remember,a NEGATIVE earth car will rust less than an old
    positive earth.Something to do with the oxidation process being the 
    transfer of electrical "thingy`s" (Ions or something) where with a 
    negative earth car the "flow" was in the right direction where it
    supplemented any "thingy`s" lost in the oxidation process thereby
    slowing down the "rusting" process.But then this was O-level Chemistry
    and a few years ago so good chance I`ve got it the wrong way round
    altogether!
                         Dougie

Re: .7

As the electrical system has insulated wires and simply uses the bodywork
as a common return, there's little chance of there being any electrolytic
corrosion.  Impressed current cathodic protection is only effective on
things like underground pipelines.

jb

    My wife put the battery into my minor backwards after recharging it and 
    it worked for 3/4 weeks without any problem, I noticed it and changed it
    back,that was six months ago, no problem since, what would this do to a
    modern car?
    On the other hand, maybe it was in incorrectly the first time and that
    was why the battery was going flat originally. (hen or egg syndrome?).
    I suppose the question is , how can I tell if my minor has been
    electrically changed over already???
     

    
    One reason for moving from +ve to -ve earth is the spark goes from the
    central electrode to the outer edge on a -ve earth car. This saves
    errosion of the central electrode prolonging it's life ............
    
    Can't remember what the lecturer said about rust problems but he did
    say Rovers used to rust out rear wings when +ve earth and changing to
    -ve cured it. 
    
    Old Wives drive Rovers don't they ???!!!!
    
    Chris.

    
    Wasn't there some electronic gizmo about that connected to the body
    panels and supposedly (or should I say allegedly) prevented rust?
    
    Chris
    

    Someone please educate me, I would have thought that if the battery was
    connected backwards, the Battery would be charged backwards. It amazes
    me that there wasnt large amount of flames.
    
    If the battery is installed with reverse polarity, wont the starter
    motor, fuel guage etc. run backwards as well ?
    
    Confused of Reading.

    Old cars have very simple electrical systems.
    
    In particular the dynamo and starter motor are polarity insensitive.
    They have a field coil which provides the magnetic field for the
    armature to turn in. If you reverse the battery you reverse the
    polarity of both the field coil and the armature, so they still work
    rotating the same way.
    
    The voltage regulator is just a set of relays, so that will work iether
    way round.
    
    I suppose the fuel gauge will be moving iron (or hot wire ?) types, so
    they will work as well. There probably isn't a volt meter or ammeter,
    but volt meter would probably work just as the fuel gauge does. An
    ammeter would work backwards.
    
    Probably the only thing that wont work straight off will be the radio
    (if there is one).
    
    Andrew

    Thanks for all the replies. I finally plucked up courage and made the
    change (it was to simplify putting a radio in, as you probably
    guessed).
    
    I was a bit concerned about the instruments. Well that's a bit over the
    top, there is only one instrument - the fuel gauge, and that didn't
    end up working backwards as Andrew correctly predicted.
    
    
    Re:>                 <<< Note 1706.9 by MACNAS::BHYLAND >>>
       >                     -< minor/major alterations?? >-

       > ... the question is , how can I tell if my minor has been
       > electrically changed over already???
    
    I was relieved to see that you had done the same thing, albeit
    inadvertently. You obviously don't have the same battery connectors as
    I do. One of mine is the non-expanding sort with a screw down the
    middle, and it doesn't fit on the larger battery terminal without
    being reamed out, which is what I ended up doing.
    
    Dick

Someone in here said "Insulate the wires and just install the radio".  What did
(s)he mean?  To just run the wires straight to the postive and negative posts on
the battery?

This sounds to me like it would work, but I'm not sure that its that simple.

-Al

    It's not so easy to fit a radio with the wrong polarity.
    
    1) The metal box of the radio is probably connected to the wrong
    polarity, leaving you with a live box that will short against any metal
    it touches.
    
    2) The shield of the aerial cable is probably connected to the wrong
    polarity. You would have to disconnect the shield somewhere, resulting
    in poorer reception.
    
    Some radios can be used on either polarity. They have some switching
    arrangement to change which lead the case is connected to.
    
    Few modern radios do this because noone still uses positive earth do
    they ?
    
    Andrew

	Re: .-1
	>It's not so easy to fit a radio with the wrong polarity.
    
	That's very true. My brother burnt two radios when tying to do it 
	in his Triumph Herald. He tried to "Insulate the wires and just 
	install the radio" and *puff*, there was the blue smoke again...

	- Jyri -

    Here again with my non-burn Minor. I installed a radio into it lately
    and found that if you insulate the body of the radio and use a rubbery
    type of ariel it works ok. You must also insulate the wiring that goes
    into and comes out of it. BTW I have fibre glass wings on my Minor so 
    this would prevent problems i suppose. Dont ask why it works but it
    does.
    Bill (my twopennorth)
    

Well, now that I've picked up my '58 MGA, I'm going to start working on it to get
it roadworthy again.

One of first things that I'd like to do is to convert the electrical system
since its been disconnected for 10 years, I might as well connect it up the way
I'm going to use it.

I've read all of the replies to this note, and the only thing that I'm wondering
about is the fuel gauge...Dick said that it didn't work straight away.  Did
swapping the wires fix it, or did the change toast the gauge??

-Al

    Sorry about the confusion. .14 was my roundabout way of saying I had no
    problems with the fuel gauge. See .13 for Andrew's explanation.
    
    Dick