(Possibly OT) Positive or Negative earth?

[Graeme]

Been playing with my '68 Traveller this morning, and finally got the engine running, but I'm still not sure whether it is positive or negative earth. It was positive earth when it left the factory, and I'm fairly sure has never been changed to negative, but how can I tell, just by looking at it? The coil has been changed, and that will work either way round. There are no helpful stickers, the no battery, until I fitted one this morning.

The engine runs, and the ignition light went out, so that answers my question?

[George]

Normally looking at the battery terminals should reveal its polarity or looking at the radio terminals?.

[meow2222]

connect a multimeter or lightbulb from each battery terminal in turn to the chassis. The terminal that lights is the oposite one to the one connected to the chassis.

NT

[George]

?

[tony sayer]

Good idea. I used to modify old Minis and suchlike and most of the time it was just reverse the battery and flash the coils of the dynamo a couple to times and that was that!..

And reverse the ignition coil, it seemed to work better the right way round;!..

[Dave Plowman (News)]

Yes. If the ignition light goes off the dynamo is charging. Which it won't with the battery reversed.

The coil should be correctly polarized to work properly, though. If negative earth this means (+) to ignition switch, (-) to CB.

[Graeme]

In message , George writes

Radio? What is this modern invention of which you speak? :-)

No radio, and there wasn't a battery until I fitted one this morning. I have fitted the battery positive to earth, which I *think* is correct.

[Graeme]

In message , [e-mail] writes

Doesn't that pre suppose that the battery is already fitted? There hasn't been a battery in the vehicle for nine years, and now I've forgotten which way it goes. Yes, I know I should have labelled it before removing the old battery, but, at that time, storage was supposed to be temporary, and short term ...

[Graeme]

In message , "Dave Plowman (News)" writes

Thanks Dave. That is *exactly* the confirmation I hoped for.

Exactly as it is wired, which cheers me up no end. The previous coil exploded about ten years ago - I've never seen anything like it, before or since. All the oily gunk inside escaped, after which it failed :-)

[George]

Hah! you have the poor mans Mini ie the dashboard was just a hole with a speedo in the center.

Mine was customized with a radio and eight track and all sorts of fairy lights :-)

[Graeme]

In message , George writes

Whoops! My mistake - I should have clarified. Not a Mini Traveller, a Morris Minor traveller, but, yes, fairly basic. Two glove boxes, one either side of the speedo - the one on the passenger side even has a drop down flap!

I do have a positive earth radio to fit, but am worried about drilling a hole in the wing, for the aerial. Just one slip ...

Reminds me of my Anglias, but we probably don't need to go there!

[John Stumbles]

Where do you get one of those these days - or is it of a vintage with the motor?

[George]

Visit many of the forums on internet that still have classic cars and sommeone might part with one at a price. :-)

When I left school,took job in a lemonade place and in the large storage shed where the emtpy damaged wooden crates were stacked somone had created a space with most of the crates to form a housing around an E-type Jaguar(could have been a Bently?) I happen to accidently find this,it was of the wire wheel type and it was as though it was still in showroom condition as it had tarpauiln draped over it. My god! the interior still smelled of new leather and the walnut dashboard and trim still highly polished.

This must have been worth a considerable amount at todays standards?

[Owain]

Wasn't it about the 1970s that oily gunk got replaced with magic smoke?

Owain

[The Natural Philosopher]

Fairly sure they work either way, there being nothing polarised in em at all.

Even the dynamo will work 'backwards' as it relies on a bit of field current to kick it into play: if that is backwards, chances are it will start up revers polarity as well!

ISTR 'flashing' dynamos to get them to prioduce DC in teh other direction.

Anyway, if the battery charges when its running, you are there. I cant think of any semiconductors IN that era of car.

[Graeme]

The one I have came from an auto jumble, and is probably the same age as the car (1968), if not older. Strangely, the most difficult part was finding one speaker. No-one, but no-one, seems to sell car speakers in anything other than pairs these days.

[Tim Lamb]

ISTR some issue with electrolytic corrosion. Didn't Mr. Ford experiment with changing battery polarity and discovered the bodywork rotted instead of the wiring?

regards

>

[Tim S]

Graeme coughed up some electrons that declared:

Ah, that brings back memories... Have you *ever* seen the oil filter bypass warning light come on on one of those (Second amber light on speedo dial)?

BTW - if you need a valve spring compressor, I may have just found one during a house clearance...

Cheers

Tim

[Roger]

The message from John Stumbles contains these words:

I had an either/or that I adjusted to the other polarity for my brother-in-law to fit in his car but he never fitted it. I rather think I junked it when he gave it back to me 10 years or so later. Perhaps I should have kept it. Given my appalling memory perhaps I did. ;-(

[meow2222]

Yes, I did presuppose that, wrongly I now see. If no battery one could fit a totally flat battery and push start it, and it will charge it. If its charging the wrong polarity, reversing the battery will help it perform & last as well as designed.

Re pos earth radios, in principle its not hard to use a neg earth radio in a pos earth vehicle, the main deal is to mount it with radio case insulated from chassis and break the aerial screen at the end near the aerial. Thick robust plastic film helps insulate the case. But of course I'm sure you'll want a real period radio, not a modern neg earther.

NT