Hi. How can I tell whether my car is wired positive or negative earth?
There is no battery, and the new battery would easily fit either way
round - the leads are long enough. The car left the factory positive
earth, but could have been changed. No, no radio either.

Presumably the car would run with the battery wired either way? The
only damage would be to the battery? There must be a way to tell which
way it should go?

Thanks!
--
Graeme

On Mon, 28 Aug 2006 18:51:00 UTC, News <news (AT) nospam (DOT) demon.co.uk>
wrote:

: Hi. How can I tell whether my car is wired positive or negative earth?
: There is no battery, and the new battery would easily fit either way
: round - the leads are long enough. The car left the factory positive
: earth, but could have been changed. No, no radio either.
:
: Presumably the car would run with the battery wired either way? The
: only damage would be to the battery? There must be a way to tell which
: way it should go?

Do the battery leads have proper positive and negative clamps on the
end? It's a reasonable indication, but not certain. If it has any
electronics fitted it's probably negative earth.

Wot I'd do, guv, is attach a voltmeter to the dynamo output and earth,
give it a spin in the normal direction of rotation, and see whether
the output is positive or negative.

Ian

In article <4VoJ9PBUsz8EFw9P (AT) nospam (DOT) demon.co.uk>,
News <news (AT) nospam (DOT) demon.co.uk> wrote:
The coil if a replacement might be marked +/- rather than sw/cb?

However, if it's a dynamo car with no electronics just try the battery
either way. You'll do no damage. It simply won't charge if the wrong way
round.

--
*Work is for people who don't know how to fish.

Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.

In message
<cCUlhtvFIYkV-pn2-8uvGjRgni4Mt (AT) internal (DOT) RFC1918.telecomplete.net>, Ian
Johnston <ian.groups (AT) btinternet (DOT) com> writes
A '68 Traveller, before electronics were invented :-)
Battery terminals are both pole, or circular, type.
--
Graeme

In message <4e5d9f0f1bdave (AT) davenoise (DOT) co.uk>, "Dave Plowman (News)"
<dave (AT) davenoise (DOT) co.uk> writes
Ah! Yes - but which way should it be, i.e. does + or - go to the
distributor?
--
Graeme

On Mon, 28 Aug 2006 20:02:48 UTC, News <news (AT) nospam (DOT) demon.co.uk>
wrote:

: In message
: <cCUlhtvFIYkV-pn2-8uvGjRgni4Mt (AT) internal (DOT) RFC1918.telecomplete.net>, Ian
: Johnston <ian.groups (AT) btinternet (DOT) com> writes

: >Do the battery leads have proper positive and negative clamps on the
: >end? It's a reasonable indication, but not certain. If it has any
: >electronics fitted it's probably negative earth.
:
: A '68 Traveller, before electronics were invented :-)
: Battery terminals are both pole, or circular, type.

One should be bigger than the other. Buggered if I can remember which
is the big one, though.

: >Wot I'd do, guv, is attach a voltmeter to the dynamo output and earth,
: >give it a spin in the normal direction of rotation, and see whether
: >the output is positive or negative.
: >
: That is so obvious! Thank you.

Ay thang yew.

<Takes bow>

Ian

On Mon, 28 Aug 2006 20:04:35 UTC, News <news (AT) nospam (DOT) demon.co.uk>
wrote:

: >The coil if a replacement might be marked +/- rather than sw/cb?
:
: Ah! Yes - but which way should it be, i.e. does + or - go to the
: distributor?

On a positive earth car, sw goes to the switch and cb to the
distributor (contact breaker). On a negative earth car + goes to the
switch and - to the contact breaker. The high tension is earthed to
the contact breaker side (not the casing) and is wound in opposite
directions in each case, so the spark goes the same way across the
plug gaps regardless of LT polarity.

In theory it therefore matters that the coil polarity is correct. In
practice, for things like Minors, Heralds, Minis, Beetles and the like
it doesn't matter a hoot.

Ian

In article <HiZ2gHDTx08EFwob (AT) nospam (DOT) demon.co.uk>,
News <news (AT) nospam (DOT) demon.co.uk> wrote:
The contact breaker goes to earth so this would be connected to the
positive of the coil on a positive earth car.

--
*Honk if you love peace and quiet.

Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Ian Johnston"
<ian.groups (AT) btinternet (DOT) com> saying something like:

The Pos is the bigger one.
--

Dave
SE6a

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember News <news (AT) nospam (DOT) demon.co.uk>
saying something like:

Make it neg earth anyway. Disconnect the dynamo, connect up the battery
as neg earth and polarise the dynamo by stroking the field terminal with
a pos lead a few times. Reconnect and start up.
--

Dave
SE6a