What makes a “good” ground?

What makes a �good� ground?

I'm sure this is a dumb question but here goes anyway.

Can paint interfere with good grounding? Do you need bare metal to bare metal? I've had problems with one dim head light and I was going to clean up the ground at the front by cleaning up all connections with a light sanding including where it grounds to the body, but if I sand to bare metal I'll be inviting rust.

Bare metal to bare metal makes the best ground - to prevent rust either: Use dielectric grease liberally on all surfaces or paint the ground AFTER you have made the connection.

Steve: Eric is right. A good ground has both mechanical (metal to metal) and electrical (the physical connection of the wire to the connector or grounding lug) components. Dielectric grease is a good idea. I use Vaseline as it is more readily available. Cleaning and lubricating the threads of the grounding screw is also important. Remember that the wire has another connector at the opposite end - that's at the lighting fixture. Those connections should be treated ion much the same way. So, make good use of steel wool or sandpaper to clean the paint off the surface of any connectors, ground lugs, etc. and use some good lubrication on them all. You'll find the problem that way. AL Bradley

Good points from both Eric and Al. Dielectric grease is okay, vaseline is as good in that situation. A dielectric material is an insulator but when used in a grounding situation it doesn't much matter, since tightening the parts creates a metal to metal contact and displaces the grease. If you really want to go overboard, use a conductive grease, if you can find some. The main thing, as stated above, is a good bare metal to bare metal junction, protected by some kind of goo to keep moisture out.

What I like to do with some grounds like the under the car in the rear one is to sand it bare, make the connection and then clear coat the area so I can keep and eye on it and make sure it is still good and clean. It has worked so far.

One other thing to be aware of is the effect of dissimilar metal joints which can result in galvanic corrosion. It is best to use steel-to-steel, and keep the moisture out! Avoid using an aluminum-to-steel connection, especially where moisture may be present! Also, be aware that use of stainless parts can have this effect. Typically it is not a problem as stainless has similar conductive properties to steel (similar "nobility") but stainless steels vary tremendously in their composition - just my 10c

<http://www.alvordpolk.com/catalog/dept.asp?id=112>

Along with dielectric grease. Grounds should be good for another 30 yrs. After you get all the ground points fixed you may want to contact British Wiring for some new Lucar connectors. <http://www.britishwiring.com/CAT14_15.PDF>

A pack of #311 and #312 will do nicely.

Wow, thanks, lots of info.

Now I just have to find a decent size tube of dielectric grease. My local Canadian Tire only sells tiny little tubes you cut open - one time use kinda things.

Al mentioned Vasiline. It works, comes in various sizes, and the store brand cost about $1 for a lifetime supply for your MG.
I don't mess with the high$ parts store dielectric grease.

Ed

I always thought a Englishman made a ground with a bare wire and a piece of chewing gum.

FWIW, the dim light on my B turned out to not be a ground after all, despite my best efforts to convince myself it was. It turns out it was a bad lucas connector going to the light subharness. Look right by the horns where there's a snakes nest of wires and connectors. Find the one for that bulb, and that's it... I do think it was the ground connector, not the power connector.

Thanks Baxter, if the clean up of the ground doesn't work I'll look at that. When you say a bad connector did you have to replace it or just clean it up?

I haven't looked at a wireing diagram yet but both my left from head light and left front running light are dim. I assumed it would be a common ground. I was going to clean up all the connections associated with the two anyway.


Steve D
'70B

when you get to bare metal and make the good ground, seal it with silicone over the entire connection a little dabwill do.

I'm going to replace it. Cleaning it was a waste of time. Lasted about two days. The connectors are too cheap to waste time trying to clean them.