Converting a positive earth system to a negative earth system

Hi All,
Started rewiring the Kogzbilt project (1956 Karrier Bantam), turfed all the old POSITIVE earth rats nest out and intend rewiring it to standard NEGATIVE earth.
As I've already repowered it with the diesel, really pretty basic.
Already have a temporary dash installed so I can start/run it.
Going to use capillary type /manual type gauges for oil/water/manifold pressure/transmission pump pressure etc. So, most wiring to be done is as I said, pretty straightforward.
Main positive in to a terminal/fuse/circuit breaker block, return line from alternator outlet back to battery.
Fuel shut-off and manual over-ride switch for electric radiator fan.
Looked at an 8 or 10 fuse/circuit breaker block with spade terminals to simplify wiring, will wire things like headlights and radiator fan through relays.
As I already have new electronic (VDO) speed and tacho, they came with instruction sheets, so even a buffoon like me should be able to follow.
Original dash had what looks like a few ballast resistors up behind the rather primitive/basic gauge set-up, so I'm assuming that won't become an issue, or at least I hope not.
Just looking at the old original wiring, it looks to me like all the original lights, headlights/taillights/indicators etc all were individually set up with the return (earth??) wires coming back to the one point.
So, as long as when it comes to rewiring these same lights, as long as I use new cables, should be able to do the same??
By that I mean instead of earthing the said lamps through the actual body, gang all the return earth wires together and bring them back to a central point and then earth them to the chassis??
I'm not a rivet counter, I've modified this old girl so much that the only things original are virtually the basic chassis and cabin, so as long as the electrics work, I'd be happy.
Anyone else who has done a system conversion from Pos-earth to NEG-earth can maybe tell me if there's anything I should be aware of, would be much appreciated.
I do have a wiring diagram to suit the larger Gamecock model, also POS-earth, but it won't be much use to me. Even the fuel tank sender and gauge have been, or will be changed over.
Thanks in advance for any help.
Just as an aside, rewired an old Jeep many,many years ago, and although being a NEG-earth system, had a similar setup where all the earth wires from headlights etc came back through the wiring loom to the fuse block on the firewall, then a reasonably thick earth cable down to a point on the chassis.
Dave_64

Just having a rethink about the idea of collecting the earth wires and bundling them together to some sort of terminal block, then to a chassis point.
If I have a crook joint or dodgy earth somewhere, may be a major job trying to isolate which one??
So, would I be better off simply earthing each component directly to the body??
Maybe someone has a very simple diagram for NEG-earth systems, or a link to one??
The simpler the better.
Thanks, Dave

Dave

This is about as simple as you can get - 1954 Dodge. Old enough to be really simple but modern enough to have some relays for good lighting etc.




This is the absolute basic. 1942 Chevrolet Blitz. A single wire alternator will cut out all the generator/regulator circuit to simplify even more. It has a mechanical starter so you need to run a wire from a starter button to your electric starter solenoid.

Magic! Thanks Lang, reckon I can work with either or both. Much appreciated. Dave

Dave, the best way to set up a common earth is to put an eye terminal on every wire, and weld a small bolt in the desired position. This way, any earth problems are common to one place, it’s easy to maintain and additional wires can be added with ease.

To limit any issues in the future, I recommend using “weatherpack” connectors for every connection and any exposed connections, like on the eye terminals, should be soldered and have dual wall (glue) heat shrink fitted. It will cost more than cheap, crimped fittings but will be so much more reliable.

I'm with DD
Use Stainless bolts and nuts to reduce the chance of corrosion . If you cannot weld the bolts, clean the area well and use stainless washers either side then a nut to lock it into position. Apply a good sealer over the bolthead and nut. Use more washers and nuts to hold the terminals to the bolt.
Cheers Steve

And of course, you really need to electrically bond your panels, if your headlights earth is to the inner guard, then make sure it is electrically connected to the chassis or battery earth terminal. I have seen rusty old things with a fair volt drop from rusty panels back to the battery. Some vehicles. eg my 1990 F250, has flexible copper braids to some panels, more for RFI (radio frequency interference} but ideal for this purpose.

By the way, there is no real difference between a positive earth system and a negative earth system in an old truck. Swap the coil wires over if you like, flash the generator and the job is done, ammeter if you have one will read backwards unless you swap the wires.

Paul

Paul,
in my application, the original petrol engine has been swapped for a diesel, which had an alternator on it already.
But good tip re the braided copper earth leads.
Just on that tip about the ammeter, I have a couple I can pick from to install, a few blokes reckon that a volt meter is just as good, albeit different use of course, but saves running heavy wires all the way to the dash. Can always run both, space permitting.
But thanks, anyway.
Dave

Jaycar do an LED volt gauge Dave, dunno if it's the right look for you but it's a handy thing to have. www.jaycar.com.au/panel-surface-mount-le...ter-5-30vdc/p/QP5582