Classic cars forum & vehicle restoration.

[47Jag]

Don,

I think that was probably the reason for the change. The only problem is that it's the wiring that corrodes now. When you strip the insulation from a 'modern' the wires are black as opposed to clean copper and need thorough cleaning before they will take solder.

Art

[Jim.Walker]

Not sure about that argument Pigtin. The reason I was led to believe was that the +ve earth connection always became very quickly and badly corroded (which I know for a fact) and that changing to -ve earth dispersed that corrosion around every electrical connection on the car.
I don't know whether the modern spate of bad electrical connections has anything to do with that or whether that is down to the cheap push-on type Lucar connectors so common these days, but it was at least easier to to keep just one battery connection clean.
Or was it a portent of EU regs./influence? All post war continental cars have always seemed to have -ve earth.

A final, deciding factor, must have been that -ve earth solid state electronics are much easier and cheaper to produce.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[pigtin]

I was not presenting an argument Jim, just stating what the thinking was fifty years ago.
Many thought , at the time, it was a conspiracy by motor manufacturers
to shorten the lives of the cars.

http://www.theanswerbank.co.uk/Motoring/Question162250.html
_________________
Due to the onset of my mid eighties I'm no longer sprightly and rarely seen in my Austin special. I have written a book though. https://amzn.eu/d/7rwRRqL

[Jim.Walker]

Not arguing Pigtin. Just that the reason I was given (or read - 50 years ago) was as I stated. Boats can suffer from electrolytic corrosion - most by the way seem to have negative earth - so why not cars? I'm still not sure that positive earth was a bad thing except where modern electronics are concerned. Even the EU bit was tongue in cheek.

I can't check what your link is about - I get a page not found error.

Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[47Jag]

Jim,

I haven't worked on many boats but the ones that I have worked on were double pole. I.E. insulated return.

Art

[giles]

Well, I took the Super Snipe on the first longish drive since I bought it. From NW London down to Bristol on Friday and then back this afternoon.

Went OK, apart from:

Got as far as around Reading on the M4, doing about 80 on the motorway, suddenly the generator warning light comes on and stays on.

My first thought was that the fanbelt had broken. I pull off at the next junction and check - the belt is still in place.

Some sort of fault with the dynamo or its regulator box. Made it to my dad's house just running the battery down, then recharged it with a charger for the drive back today.

I think I feel a swap to a modern alternator coming on.......

[peter scott]

I know that brush wear should be at a slower rate in an alternator but if you aren't planning to use the Snipe as your everyday transport then you probably wouldn't find any difference in reliabilty. If you replace the brushes in your dynamo you probably won't have to replace them again for another 80 to 100k miles. The three spool regulators (as in your car) are not as easy to tamper with as older types and generally survive unmolested.

The rectifiers and regulators in alternators are common causes of failure.

Peter
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http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[pigtin]

I fitted new bearings and brushes when I restored my Austin 10/4 in 1985. It's done over 30k since then and never a flat battery or any other problem.

Don.
_________________
Due to the onset of my mid eighties I'm no longer sprightly and rarely seen in my Austin special. I have written a book though. https://amzn.eu/d/7rwRRqL

[petelang]

I recall from many years ago, that if you convert the polarity from pos to neg earth and do not repolarise the dynamo correctly then the cut out contacts start to chatter in the control box and it burns the contact points off. If your car has been converted you should check and repolarise the dynamo. Look at the control box (regulator) contacts and see if there is any burning.
When I was an apprentice we had lots of repeat failures when DIY mechanics were doing this job and wrecked sucesssive regulators before they came to us for the proper cure.

[giles]

Well, back in early February I got this auto electrician to fit an alternator.

No probs now, no more flat batteries. Regulator box redundant. Ammeter pretty much redundant since alternator is charging pretty much all the time.