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A warning for all pre war owners.....

JedFurneaux
Posts: 35
Joined: Tue Jul 11, 2017 5:50 pm
Location: Tregoss Cornwall

A warning for all pre war owners.....

Post by JedFurneaux » Sat Aug 24, 2019 9:14 pm

Hi all.
My 1934 LQ2/20 has had a busy Summer with shows and has given no problems. After two idle weeks I went to start her up today to find the battery was flat (and I mean absolutely dead). I know the battery is good and the charging system is working as it should so this was a real mystery.
I substituted a spare battery but when connecting I noticed some wisps of smoke coming from the positive lead about three inches from the terminal and where it enters the flexible armoured sheathing. This sheathing became too hot to touch within seconds and it was obvious that there was a short. Upon examination I could see that the original (85 year old) cable insulation had deteriorated to the extent that the inner cable was able to make contact with the armoured sheathing where it emerges from the ferrule which of course is a conduit to earth as it is bolted onto the chassis in several places. This would explain the dead flat battery but a more sinister issue is of course the very real risk of fire which had the potential to consume the car, garage, tools and two fine classic motorcycles!
I'm sure the armoured sheathing was a very fine idea back in 1934 and to be fair it has lasted all this time but of course it poses a very real fire risk if it allows the battery lead to short when the cable insulation deteriorates.
I therefore mention this as a warning to all owners of vehicles so equipped to check their battery positive cables for similar deterioration. I was lucky this time.

John Hitchins
Site Admin
Posts: 211
Joined: Mon Feb 08, 2016 10:52 am
Location: Wellington Somerset

Re: A warning for all pre war owners.....

Post by John Hitchins » Sat Aug 24, 2019 9:40 pm

Thanks for that, I have never checked the battery cable as it cannot be seen easily so out of mind. Another thing to check on my DB18 which must be similar.

Christopher Storey
Posts: 256
Joined: Wed Mar 16, 2016 6:40 pm
Location: Cheshire

Re: A warning for all pre war owners.....

Post by Christopher Storey » Sun Aug 25, 2019 7:58 am

In my innocence I would have thought your car would be positive earth . Has yours been converted to negative earth ( or were these negative earth originally ) ? If not, your short is somewhere else, which is even more sinister

JedFurneaux
Posts: 35
Joined: Tue Jul 11, 2017 5:50 pm
Location: Tregoss Cornwall

Re: A warning for all pre war owners.....

Post by JedFurneaux » Sun Aug 25, 2019 11:27 am

Hi Chris, yes....mine is negative earth and the fault is definitely caused by the cable insulation having broken down allowing the inner to contact the armoured conduit. By the looks of it I would say that mine has always been negative earth although I'm happy to be corrected by those who know better.

New Dexter
Posts: 380
Joined: Fri Feb 12, 2016 9:41 am

Re: A warning for all pre war owners.....

Post by New Dexter » Sun Aug 25, 2019 11:44 am

I may be wrong but I thought it was the case that pre-war cars were negative earth and at some time, possibly after WW2, that cars became positive earth. Then the more modern cars reverted to negative earth. There must have been a reason to change but it would be interesting to know why it went from negative to positive and then back to negative.

JedFurneaux
Posts: 35
Joined: Tue Jul 11, 2017 5:50 pm
Location: Tregoss Cornwall

Re: A warning for all pre war owners.....

Post by JedFurneaux » Sun Aug 25, 2019 1:57 pm

There was definitely some advantage in having negative earth.... I remember reading that it is something to do with how electricity works but don't ask me to explain it!

classiclife
Posts: 397
Joined: Wed Sep 05, 2018 9:55 am
Location: Ridgewood - East Sussex
Contact:

Re: A warning for all pre war owners.....

Post by classiclife » Sun Aug 25, 2019 3:04 pm

I have heard, from time-to-time, that +earth vehicles were LESS prone to rusting. I cannot recall why, but allegedly there was a scientific rationale for stating such.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Area Representative.

Southern Classics Society Events Co-ordinator.
www.southernclassics.org.uk

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John-B
Site Admin
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Joined: Tue Feb 09, 2016 9:10 pm
Location: Salisbury, UK
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Re: A warning for all pre war owners.....

Post by John-B » Sun Aug 25, 2019 3:40 pm

I thought it was because positive earth causes a messy corrosion around the battery terminal.

Petelang
Posts: 216
Joined: Sat Feb 13, 2016 10:23 am
Location: Nottingham
Contact:

Re: A warning for all pre war owners.....

Post by Petelang » Mon Aug 26, 2019 12:53 pm

The change to Negative earth more recently (60's) was due to the advent of electronics in components such as transistor radios, regulators and electronic ignition as it was grossly more expensive to make components for positive earth. Nowadays, all electronics are pretty much cheap as chips, but then they were large, easily damaged and more costly.
The change to positive earth before was an attempt to reduce corrosion in the much wider used steel bodies as where cable looms ran through bodywork, a magnetic field is created which exacerbated corrosion. That combined with zero corrosion protection, waxoyl coating and the ever thinning metal used led to Fiat's that vanished before your very eyes, and the like.
That's what I was told as an apprentice many years ago.
Peter
Peter Langridge
Cloud Nine Classic Weddings, Nottingham.

NickDeAth
Posts: 343
Joined: Mon Feb 15, 2016 8:41 pm
Location: South Essex

Re: A warning for all pre war owners.....

Post by NickDeAth » Mon Aug 26, 2019 8:48 pm

I seem to remember something about anodes and cathodes but the detail is lost in the mists of time!

Nick
"Nick - do you think you will ever put that old car back together again?"

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