Club 80-90 Forums

If my CD player, which is on the leisure battery circuit, shares an earth with my cigarette lighter socket, on the starter battery circuit; could this cause any problems?

No earth is the body all batteries and circuits connect to the body on the neg side.

No

too slow......

Thanks both, That's what I figured, just thought I'd double check!

Just as a useless quick quiz ( I'm bored at work) who can name a car that used to have a positive earth system and why it was swapped to being commonly a negative earth set up....

I can remember a little, I still have a little polarity converter box for a car radio for one of those vehicles knocking about somewhere. Late 60's it came into my spares! Other than that my memory seems blank.

I'm fairly sure I had a positive earth car but not sure which one it was. I think the oldest I had was a Mini van with floor starter, sliding windows etc. Think my MGB was negative earth (1965) Had a Wolseley 1660 and Triumph Herald so could have been one of those. Seem to remember changing one car from positive to negative earth as well.
Think the change was something to do with corrosion? Made it easier to fit a radio as well.

Healey 100/4?

My mother had a Healey convertible heap for a while - Sprite? - may have been for that? ( I remember it went a lot better after I cleared all the dirt from under the accelerator pedal! )

My 1968 cooper S still had positive earth when i bought it back in 2006. Converted it to negative earth during the engine refurbish SOLD now

pionte wrote:Just as a useless quick quiz ( I'm bored at work) who can name a car that used to have a positive earth system and why it was swapped to being commonly a negative earth set up....

Almost everything used to be +ve earth - the change from dynamos to alternators was the main reason, although a quick google suggests you can convert alternators to +ve earth for upgrading charging without gonig to the hassle of converting everything.
http://mgaguru.com/mgtech/electric/et098.htm" onclick="window.open(this.href);return false; seems to give a reasonable explanation.

Yes as everyone has correctly answered... Most cars used to be + earth, my first encounter was a 1963 Austin mini... It was my sisters and as I had just started my mechanics apprenticeship I decided to put a 1275 GT engine in place if the weezy 850cc it came with, it wasn't until I connected everything up I had problems.. From memory I just swapped the terminals around and binned the radio.. I must have done something with the dynamo but can't remember quite what. When I asked my tutors about why the change they told us it was because of corrosion and the flow of electrons... I'm not sure as a 16 year old 1st year apprentice I fully understood it. I loved that car though... The floor mounted hi low beam switch and sliding door windows.

pionte wrote: I must have done something with the dynamo but can't remember quite what.

You just "flick" a live +ve feed from the battery across the "F" (= Field) terminal a couple of times (it makes a bit of a spark !). This re-polarises the dynamo so it becomes negative earth. You also need to reverse the LT wires on the coil.

pionte wrote: When I asked my tutors about why the change they told us it was because of corrosion and the flow of electrons...

Correct

My 1956 BSA 500cc single is +ve earth. You do have to think twice when working on it's electrics as you get so used to everything being the "normal" way around !