Properties of wire used in harness?

[David_Doan]

If you're just replacing existing wire due to frayed or damaged insulation, just replace with the same size wire or bigger. Easy way to find the size (gauge) is to strip the insulation back and find the smallest hole on your stripper that does not grab the strands when you strip it. I think most of the bugeye stuff is 18 or 16 gauge. If you change the color from original, label each end of the splice.

Everything on the bugeye is just straight DC except for the tach, no fancy wire required. When in doubt use bigger wire. None of this is rocket science. These cars have a pretty poor electrical system, mostly due to the bullet connectors that turn green and corrode. If you're have any problems, clean/replace all of those 1st. The biggest offenders seem to be the ones routed through the bonnet for the lighting system.

 

[Bayless]

The answer on the bullet connectors is electric grease, available at your favorite auto parts store or electronics supply. It will last many years.

 

[Sarastro]

I think David's quite correct. It's not a big deal--just replace with the same size or, if necessary, a little larger. Document everything and there should be no problems in the future.

Connectors are really a problem. Those bullet connectors are trash. Replacing them with something else isn't a bad idea. I'm not a fan of greasing electrical connections, because if they are done right, it's not necessary. No one does this in other environments (e.g., military specs) even when they are as severe of more so than automotive.

I'm not using any bullet connectors in my MG. I rewired it myself, without a purchased harness. The colors are not standard, but it's well documented, so any future owner should have no problems. Most of the wiring is no. 16, with no. 14 in some of the higher current parts of the circuit. No. 16 is fine for headlights (I have separate conductors for each light, though); I'm quite sure that the headlight wiring in the replacement harnesses is not no. 10, although it might be 14.

https://www.nonlintec.com/mgtd/electrics/#wiring

I also moved the battery ground to a more sensible location and implemented a single-point ground system.

https://www.nonlintec.com/mgtd/engine/#reinstallation

I did some similar things on my bugeye (which, alas, I no longer own). My treatise on the electrical mods begins with a discussion of fusing, which I think is worth reading.

https://www.nonlintec.com/sprite/electrical/

Anyway, this is much more than you need to know to answer your question, but maybe it's still of interest.

 

[Keoke]

The answer on the bullet connectors is electric grease, available at your favorite auto parts store or electronics supply. It will last many years.

Well if they didn't collect dirt before they sure will now.

 

[Keoke]

I also moved the battery ground to a more sensible location and implemented a single-point ground system

Single point ground systems also called Golden Spike require an unusually large amount of wire and have the highest Resistance possible.
A grounding wire will not exhibit the low resistance of the more massive vehicle's structure.

 

[MGNoir]

Interesting stuff Sarastro - I do a lot of things with Arduino single-board computers and have been tempted to refactor some aspects of my car's electrical system, including some computer control. But at the same time in my case, if it aint (that) broke...

So far I've just been sticking with replacing all the spade connectors with brand new ones, bullets too. Was under the car working on the oil pan and saw how oily and loose the wires were running underneath I think for reverse. Also one bullet connector down there that doesn't go to anything.

 

[Bayless]

If you're really concerned about collecting dirt then you have been way too sloppy in using the grease. It only tanks a little bit and should be inside the cover.

 

[Keoke]

If you're really concerned about collecting dirt then you have been way too sloppy in using the grease. It only tanks a little bit and should be inside the cover.

OF course that is the problem.
However, since grease is a dielectric why should you put a dielectric in an electrical connection????:friendly_wink:

 

[Sarastro]

Single point ground systems also called Golden Spike require an unusually large amount of wire and have the highest Resistance possible.
A grounding wire will not exhibit the low resistance of the more massive vehicle's structure.

I'm not sure that's true, in general. If I were to ground the headlights in my TD, for example, at the fender, the current path is through a very thin sheet of steel, a fairly high-resistance material, and into the frame through a couple of places where bolts' lockwashers managed to break through the paint layer. Contacts, especially small ones, always have higher resistance than solid metal; in fact, in auto wiring, the electrical contacts usually have most of the resistance, not the wire. This is one reason why ground problems are so common.

In any case, it's all pretty academic, since, with any degree of care, you can keep the wiring resistance low enough that it doesn't matter. More important is the reliability of the connections, and using local grounds is probably the worst choice, in that respect.

Interestingly, my Bugeye had a single-point ground on the firewall for most of the high-current wiring. I don't know if it originally was that way or it was just the wiring harness installed when the car was restored sometime before I bought it.

 

[Sarastro]

However, since grease is a dielectric why should you put a dielectric in an electrical connection????:friendly_wink:

Well, the theory is that it prevents corrosion and moisture infiltration. When you make the connection, the pressure is strong enough to force the grease out of the way and allow a metal-to-metal contact. It's kinda like switch design--switch contacts are designed to "wipe" slightly as they make contact, so each time the switch is closed, the mating surfaces are cleaned a little.

Does the grease increase the contact resistance? It might. On the other hand, if it prevents further corrosion, it could keep the contact working when it otherwise wouldn't.