Negative earth v positive earth

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cococola
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Re: Negative earth v positive earth

Postby cococola » Wed Jan 12, 2022 8:39 am

I did think that might be the best option Mike,of going neg/earth in order to use on modern items.
So to confirm to change to neg/earth
1. change battery around in its carrier to connect terminals opposite to before.
2.Alter the coil connections over to match.
3.polarise the dynamo by 'flashing' a wire from the +ve terminal of the battery - and touch it to the small terminal on the dynamo a few
times.
Would this be all that is required to change to Neg/earth please?
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simmitc
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Re: Negative earth v positive earth

Postby simmitc » Wed Jan 12, 2022 9:16 am

If you keep the car as +ve earth, then, as per my previous post:
An older temperature gauge will be s simple moving coil device and will work fine either way. More modern gauges have electronics in them (digital display, warning lights, buzzers etc) and they will be polarity conscious, and so will not work on the wrong earth.

For your socket, it MUST be isolated from the car body. Use a wooden or plastic mounting block. If the socket already has two wires attached, then connect the red wire to the car body using an inline fuse and the black wire to a supply wire on the car. Depending on where you connect to the supply, it could be brown or green. Consider what load (watts or amps) you want to place on the socket and ensure that the socket is rated accordingly and that the wiring you use is suitable.

Also consider whether you want the socket permanently live or switched via the ignition. You may need to supply the socket via a relay.

If the socket has terminals rather than wires attached, then connect the centre terminal to a red wire and the body to a black wire, and then proceed as above.
The temp gauge is simple to wire: From the fusebox, pick up one of the fused and switched terminals and from there, run a wire to the supply terminal on the gauge. Connect the other terminal to the sender fitted near the thermostat (you have to fit the sender). For lighting, connect one wire form the lamp to the wires used to illuminate the speedo. The lamp may have one wire, earthed through case of gauge, or two wires, in which case the second is connected to earth.

You can run a radio with a dynamo, you do not need an alternator, but you would have to find an older radio that could run +ve earth.

As I said previously, it comes down to originality vs ease of use.

Steve Phillips
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Re: Negative earth v positive earth

Postby Steve Phillips » Wed Jan 12, 2022 10:41 am

One way to wire up items such as an aux socket (cigarette lighter socket), a USB charging socket, dash cam or radio is -

run a feed from the +pos terminal of the battery to a stand-alone insulated fuse block, I would have a suitable size fuse as close to the positive terminal of the battery as possible as well, something like this (lots of others available)

https://www.vehiclewiringproducts.co.uk ... e-fuse-box

Or if all your items come with their own inline fuse you could use something like this

https://www.vehiclewiringproducts.co.uk ... n-post-red

This can be mounted to the steel body of the car regardless of being positive or negative earth as it is isolated.

Feed all your new negative earth items from this supply,

DO REMEMBER to check how you new items are earthed, sometimes there will be a conductive ring in the mounting screw of a plastic cased product, these can easily be seen and are normally listed in the instructions. if you have something that earths through its mounting screw it has to be insulated away from the steel work of the car or you will be giving it 2 + positives...... assuming that everything your mounting has an earth wire / wires use something like this

https://www.vehiclewiringproducts.co.uk ... post-black

Which again keeps all your earths’ separated from your steel body that is positive, now you can run a wire back to the negative post of the battery,

Basically you have made a negative earth circuit for your car,

if you want your new circuit to be switch / ign controlled then use a standard 4 pin switching relay and run your new positive that comes direct from the + of the battery to the relay and then take it to your fuse / distribution block, to trigger the relay pick up a feed from something like the cars ign switch, connect it to the relay and then the relay to earth, now when you put the ign on / flick the switch your positive earth ign circuit will turn on a relay that will supply + positive power to your new circuits / items.

Hope that helps

Steve
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geoberni
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Re: Negative earth v positive earth

Postby geoberni » Wed Jan 12, 2022 10:57 am

When it comes to the Smiths Temp Gauge, that has it's own issues irrespective of Pos/Neg polarity.

I don't know when they started to fit the Voltage Regulator to the Minor, I think it may have been '64 when they changed the Speedo Colour.
Now there is a lot of garbage spoken & written about Electrical Temp Gauges needing to use the 10v from the Voltage Regular, essentially saying that all gauges need to.
Totally wrong. New ones yes, Old ones not always....
Smiths gauges changed over the years, and there were plenty of early models that work fine without.
If you are buying a modern new 'Smiths' type gauge and sender, then yes you will need the 10v supply, because that's what they require.
If you have a older gauge, then 'it depends'.


Really early gauges, pre-WWII, were moving magnet/coil construction.
Bimetal gauges are the most common Smiths electrical gauge. The first bimetal gauges were the “TE” type gauges introduced in the early/mid-1950s. Then there was the "BE" soon followed, by mid 60s, by the "BT". These “BT” gauges were supplied with a lower (average) voltage from the instrument voltage regulator.


There was a long discussion about temp gauges and regulators last year. viewtopic.php?f=11&t=73844&start=20&hil ... ture+gauge

Personally, my car doesn't have a Voltage Regulator and I was lucky enough to match up a modern sender with an old gauge, of the sort that has adjustment available through the back.
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jagnut66
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Re: Negative earth v positive earth

Postby jagnut66 » Wed Jan 12, 2022 7:37 pm

I did think that might be the best option Mike,of going neg/earth in order to use on modern items.
So to confirm to change to neg/earth
1. change battery around in its carrier to connect terminals opposite to before.
2.Alter the coil connections over to match.
3.polarise the dynamo by 'flashing' a wire from the +ve terminal of the battery - and touch it to the small terminal on the dynamo a few
times.
Would this be all that is required to change to Neg/earth please?
To answer your question: 1 yes. 2 yes. 3, as far as I remember, yes.
I have swapped to an alternator, so don't need to flash the Dynamo..... :wink:
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1955 Series 2: Traveller: "Elsie May" -- On the road and enjoying her 'as is' for now but I see work ahead......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)

cococola
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Re: Negative earth v positive earth

Postby cococola » Thu Jan 13, 2022 10:06 am

So I'm going to the neg/earth route and changing the battery round I have a brown wire on the starter switch under the bonnet, where the black wire was fitted. I've now fitted red on this switch... To positive and black earth to neg on the battery. Does that thinner brown wire that was on the starter switch, go to a neg or pos connection please?
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geoberni
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Re: Negative earth v positive earth

Postby geoberni » Thu Jan 13, 2022 10:28 am

cococola wrote:
Thu Jan 13, 2022 10:06 am
So I'm going to the neg/earth route and changing the battery round I have a brown wire on the starter switch under the bonnet, where the black wire was fitted. I've now fitted red on this switch... To positive and black earth to neg on the battery. Does that thinner brown wire that was on the starter switch, go to a neg or pos connection please?
What the $£&^%!!!!

Who mentioned going anywhere near the Starter Switch? I think you mentioned it was a Pull start car, not a Solenoid Start.
What Red Wire?
What brown wires are you messing around with!
As Mike already confirmed there are 3 simple steps involved, none of which require going anywhere near the starter switch! :o :o
1. change battery around in its carrier to connect terminals opposite to before.
2.Alter the coil connections over to match.
3.polarise the dynamo by 'flashing' a wire from the +ve terminal of the battery, touching it to the small terminal on the dynamo a few
times.
The only issue that you may encounter is that Battery posts are normally different sizes and clamps are marked + & -.
So you'll likely have to swap the clamps over (I hope that aren't soldered/brazed onto the cables).
Last edited by geoberni on Thu Jan 13, 2022 10:59 am, edited 1 time in total.
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oliver90owner
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Re: Negative earth v positive earth

Postby oliver90owner » Thu Jan 13, 2022 10:56 am

I think that treating/ describing circuits as ‘negative’ and ‘positive’ is clearly befuddling the OP.

IMO, it would be far simpler (and safer) to consider/describe the connections as ‘live’ and ‘earth’.

myoldjalopy
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Re: Negative earth v positive earth

Postby myoldjalopy » Thu Jan 13, 2022 11:36 am

'geobernie' - when he mentions the 'starter switch', the OP must mean the switch that the pull-start wire attaches to, as he mentions it as being 'under the bonnet'..........

geoberni
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Re: Negative earth v positive earth

Postby geoberni » Thu Jan 13, 2022 11:39 am

myoldjalopy wrote:
Thu Jan 13, 2022 11:36 am
'geobernie' - when he mentions the 'starter switch', the OP must mean the switch that the pull-start wire attaches to, as he mentions it as being 'under the bonnet'..........
Aghhh don't mention "pull-start wire", it's a 'cable' like Bowden cable, someone is likely to think you're referring to something electrical... :wink:


I realise he's referring to the Pull Start Sw, I just don't understand why he's going anywhere near it....
What's the Red Wire he's moving around, where's he moved it from?
He says
where the black wire was fitted
The past tense infers he has now moved that, to where heaven knows, but what was a Black Wire doing on the Pull Start?
All wires on a Pull Start are supposed to be Brown!
This is how people get themselves in a muddle with their electrics, they do things which nobody has even mentioned.... :roll:
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jagnut66
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Re: Negative earth v positive earth

Postby jagnut66 » Thu Jan 13, 2022 11:49 am

So I'm going to the neg/earth route and changing the battery round I have a brown wire on the starter switch under the bonnet, where the black wire was fitted. I've now fitted red on this switch... To positive and black earth to neg on the battery. Does that thinner brown wire that was on the starter switch, go to a neg or pos connection please?
As Berni said above, there is no need to touch the wiring connections on the starter motor.
Both mine are 'pull start' too.
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1955 Series 2: Traveller: "Elsie May" -- On the road and enjoying her 'as is' for now but I see work ahead......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)

simmitc
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Re: Negative earth v positive earth

Postby simmitc » Thu Jan 13, 2022 2:06 pm

Could the "black wire" be a thick battery cable from the wsitch to the starter or even the switch to the battery? No it shouldn't be moved, but it is (usually) black :-? Perhaps over the years, a red battery cable has been fitted - I know that I have used colour coded cables when renewing them.

Coco, can you post a picture of the battery and starter switch as they are now?

geoberni
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Re: Negative earth v positive earth

Postby geoberni » Thu Jan 13, 2022 2:29 pm

simmitc wrote:
Thu Jan 13, 2022 2:06 pm
Could the "black wire" be a thick battery cable from the wsitch to the starter or even the switch to the battery? No it shouldn't be moved, but it is (usually) black :-? Perhaps over the years, a red battery cable has been fitted - I know that I have used colour coded cables when renewing them.

Coco, can you post a picture of the battery and starter switch as they are now?
Could be. The 2 heavy cables are not colour identified in the manual. Just big Fat lines!
My SII has Brown from Battery to Switch, but the cable down to the Starter is unlike the rest and looks like PVC Black sleeved; I just assumed that had been replaced at some time in the past 60 odd years...
I assumed the black was a replacement since on the correct coding Black is an Earth....
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cococola
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Re: Negative earth v positive earth

Postby cococola » Thu Jan 13, 2022 7:50 pm

I originally had a red battery cable bolted to the body on the passenger side and connecting to the battery neg post.
on the drivers side I had a black cable connected to the battery +
I have now turned the battery round in its cradle and I have swapped the red wire over with the black cable (by disconnecting them) so that I have correct colours going to the correct posts,Ie red to + and black -
I don't know what has gone on before as I haven't owned this convertible very long.
The car has an ignition switch that I turn followed by pulling the starter switch knob inside the car.
The brown wire that I was referring to was connected under the bonnet on the bulkhead push start switch.This brown wire was under the original red cable and further checking today I have left the brown on its same connection as the car starts as it should and everything works correctly.
I'm sorry I made you swear geoberni :o I guess my descriptions aren't always so clear maybe, but Iam trying ..honestly :)
I did also flash the wire on the dynamo and changed the coil wires around so hopefully I have done everything as it should be??
If there is anything else that I have missed or that I can check then Iam all ears.
Although I have many years car experience it can still be a learning curve with 1963 eras and I do thank everybody for their help and advice
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geoberni
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Re: Negative earth v positive earth

Postby geoberni » Fri Jan 14, 2022 11:07 am

cococola wrote:
Thu Jan 13, 2022 7:50 pm
I originally had a red battery cable bolted to the body on the passenger side and connecting to the battery neg post.
on the drivers side I had a black cable connected to the battery +
This doesn't make any sense whatsoever.
On Jan 10th you said your car was Positive Earth, but now you have said the Battery Negative post was originally going to the bodywork.
That would be NEGATIVE EARTH!
I have now turned the battery round in its cradle and I have swapped the red wire over with the black cable (by disconnecting them) so that I have correct colours going to the correct posts,Ie red to + and black -
Did you swap the clamps over? Originally introduced in the late 60s Battery posts have been different sizes, (there are a few different specs even now) the +ve is typically around 1.6mm larger diameter, with a matching size clamp, to try and stop people connecting them incorrectly. Of course, if the car has the original old Lucas Cap type terminations, this may not be noticeable.
I'm sorry I made you swear geoberni :o I guess my descriptions aren't always so clear maybe, but Iam trying ..honestly :)
Don't worry about that, I was just concerned that you might do some damage to the car (or yourself) by getting things cross connected.
It's just that, to use a metaphor, we sometimes get people here needing water wings and while they're having basic lessons, they suddenly run and jump in the deep end with both feet... sometimes they can't be rescued because they never come back.... :cry:

From what you have written, I think you have just made the car Positive Earth :o

If there is going to be any satisfactory conclusion to this, we need photo(s) of the Battery, as it is now, clearly showing the connections.
Here's mine as I've just been out to take it in the garage (and I've just noticed from that condition indicator that it needs charging :roll: ).
This is Negative Earth.

Negative to Bodywork.
Positive to Start Sw, on the same side as the thinner Brown wire from the Voltage Regulator.
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cococola
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Re: Negative earth v positive earth

Postby cococola » Fri Jan 14, 2022 12:54 pm

Well I did think that Id explained things clearer this time but obviously not :o
I've just taken the pictures below and to reconfirm that the wire that is now red (as correctly fitted) was black previously and the black (now fitted correctly) was red. These were before my ownership.
I have also turned the battery around so that the - terminal and + terminal are on the correct sides to be negative earth.
I have also changed the wires over on the coil and flashed the small terminal on the dynamo.
Going by all of this I really thought that I had done things correctly? :-?
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simmitc
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Re: Negative earth v positive earth

Postby simmitc » Fri Jan 14, 2022 1:12 pm

That looks good :D
Red wire for +ve connected to +ve battery terminal at one end and starter switch at the other.
Earth braid strap (not black cable) connected between battery -ve terminal and car body. That is negative earth.

I can't see the markings on the coil, but it should have the white wire ignition feed to the + or IGN terminal and the white with black tracer from the - or CB terminal going to the side of the distributor.

cococola
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Re: Negative earth v positive earth

Postby cococola » Fri Jan 14, 2022 1:53 pm

Thats brilliant thank you :D Im really glad that everything is in order as neg/earth set up.
My next steps are to add the 12v socket,temp gauge for main starters.
I wonder if I was to wire up a cd stereo would I have sufficient power over time to use this or is it not worth the hassle for loosing battery power having a dynamo set up?
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geoberni
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Re: Negative earth v positive earth

Postby geoberni » Fri Jan 14, 2022 2:11 pm

That all looks fine, although I've still no idea what was going on.
You've been talking about swapping Black and Red Cables/Wires, but I don't see a Black one anywhere...?
I assume you actually meant the Braid.

Whatever you had in the past, the circuit is now correct for a Negative Earth vehicle.
It must have been a bit of a bodge to get that Earth braid onto a Positive Terminal, because it would have been a little undersize to go on the Positive Post.

Don't worry about the power consumption of a CD/Radio. My car is fine with that.
The only thing I have done in that regard was the Previous Owner fitted Halogen headlamps without fitting an Alternator, so I changed them for LED Lamps.
Halogens and a dynamo don't go together. Those are a step too far for a Dynamo. :wink:
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