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Dart polarity

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Marcus
Posts: 319
Joined: Tue Feb 16, 2016 9:06 am
Location: Silk willoughby Sleaford

Dart polarity

Post by Marcus »

Morning all, can anyone tell me whether the dart was always positive earth out if the factory or did it change to negative during the production run?
I ask as I have a car that has no battery fitted and no markings on the terminals, plus the terminals are the same size so impossible to tell which way around the battery goes and I don’t want to cook any of the electrics.
Any pointers gratefully received.

Marcus
Posts: 319
Joined: Tue Feb 16, 2016 9:06 am
Location: Silk willoughby Sleaford

Re: Dart polarity

Post by Marcus »

The car dates from 1963, so I’m punting positive. Any one care to opine?

Vortex O'Plinth
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Location: Gloucestershire

Re: Dart polarity

Post by Vortex O'Plinth »

The SP250 was positive earth throughout it's production run. The original battery terminals were polarity discriminated so if yours aren't a previous owner has changed them. If he's done that he may have altered the grounding polarity, so that needs checking. Connect the battery and turn the lights on but don't start the engine. If the ammeter shows a discharge you have the polarity correct. If it shows charge you need to reverse the battery connections.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

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JohnM
Posts: 206
Joined: Thu Feb 11, 2016 1:31 pm
Location: N W London

Re: Dart polarity

Post by JohnM »

Hi Marcus,
it would almost certainly have been positive earth if it is unmodified. In real life, if the car has a dynamo fitted and no modern electronics, it doesn't really matter which polarity you wire it it will work fine. (With the possible exception of the windscreen washers if it has an original "burst wash" Lucas Screenjet motor still fitted - that can blow a fuse because a wire needs to stay with the "live" feed, but worry about that if it happens!)
I've "converted" a couple of cars to negative earth this way to make it easier (and safer) to use modern electronics via the cigarette lighter socket.

So I'd check it hasn't been converted to alternator instead of dynamo - in which case it needs to be negative earth anyway - and then use whichever polarity you prefer. If the car is still wired up, you could look at the coil connections - the "+" should go to the distributor if it's positive earth wired (in theory!)

Hope that helps,
John

ps- I was typing this when Nick posted. I honestly can't remember whether I changed over the ammeter connections or not when I changed the polarity - Nick may well have a simple solution!
John M in Middlesex, NW London
1962 SP250 "B" Spec
DLOC Herts Region Sec

Marcus
Posts: 319
Joined: Tue Feb 16, 2016 9:06 am
Location: Silk willoughby Sleaford

Re: Dart polarity

Post by Marcus »

Thanks both, appreciate the quick response.

Ian Slade
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Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: Dart polarity

Post by Ian Slade »

Unless it has electronic ignition it doesn't matter, most electronic ignitions are negative earth, also most radios since the 70's are also negative earth, check both.
Owner since the 70's, Genghis is slightly to my left.

Marcus
Posts: 319
Joined: Tue Feb 16, 2016 9:06 am
Location: Silk willoughby Sleaford

Re: Dart polarity

Post by Marcus »

Thanks all, positive earth confirmed. Car is now running for first time since 1994!
More advice sought in next post.

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