Positive or negative earth on a rewire?

[Ivor Hawkins]

Yes I can successfully engineer virtually anything but I have electrics dyslexia, nothing seems to make any sense to me, so I need some please please chaps!

My box saloon was negative earth, If I remember correctly, I’m re-wiring with a Ruby loom and Ruby cut out, but should I go positive earth as per the wiring diagram or will things like the ammeter and petrol gauge go backwards?

I know it sounds silly, but should I also “spark” the dynamo to ensure it charges correctly?

Thanks for your help fellas, now I will try and work out why I have more wires going into the cut out than on the wiring diagram!
   

[Robert Leigh]

It is probably easier to stick with the original positive earth, so that any future reference to Austin literature willl agree with what you have done. As for flashing the cutout points to polarise the dynamo field, do it if it does not work without doing it, but you will not damage anything by quickly closing and opening the points which will make sure it is right on a 'just in case' basis. There were changing theories about corrosion with negative earth, and positive became the norm until the common use of alternators which has led to negative earth being standard. With a dynamo you can change according to choice, but with an alternator usually having a built in solid state regulator there is no choice but to follow the makers instructions.

[Bill Dixon]

Ivory, RPs are negative earth. Stick to negative earth. Make sure you have a good earth connection from the E tag on the cut out unit to the bulk head scrape away the paint to clean metal. The loom can be used on either negative or positive earth. But
I would keep a negative earth.

["Slack Alice" Simon]

The ammeter connections just need to be swapped, if it is reading the wrong way.

I think the fuel gauge doesn't care which earth it is (see current (!) discussion on the forum).

[Ivor Hawkins]

Thanks fellas, I’ve made sure I have a good earth from the cut out and checked it with a meter and I have managed to sort out the cut out wiring, the extra wires go to the auxiliary fuse for the horn and electric windscreen wiper.

Now can anyone tell me if the wiring for the rear lamps and fuel gauge runs under the car or inside, I’ve completely forgotten!

[Andy Bennett]

My RP wiring runs outside down the drivers side, no idea if routing is original.
Andy

[David Stepney]

Thanks fellas, I’ve made sure I have a good earth from the cut out and checked it with a meter and I have managed to sort out the cut out wiring, the extra wires go to the auxiliary fuse for the horn and electric windscreen wiper.

Now can anyone tell me if the wiring for the rear lamps and fuel gauge runs under the car or inside, I’ve completely forgotten!

Ivor, Down the outside just inside the drivers side lower sill that the running board is bolted to. I know this, as my car has several little steel clips bolted to the body at this position to take the cables.

[Ivor Hawkins]

Thanks Andy, I think that’s correct...I have since had a trawl through the forum and found that Nick Turley’s RP is positive earth and apparently always has been!

[Parazine]

Positive earthing system introduced 6th December 1935 at chassis number 236210.

(R J Wyatt "The Austin Seven, the motor for the million", David & Charles, 1972. P185)

[Bob Culver]

My RP is neg and always has been. It lessens risk of persons conecting battery wrong way around.
I think it was established here that the corrosion ideas relate to the wiring in its porous cotton coverings, not applicale to plastic wiring. Whatever, the factor is neglegible.

Bemused at use of fellas. I have often used fellahs as a local joke. A common expression by local maori youth is/was "yous fellahs"