Hah! Good story Chuck. Very common thread among rewirers-of-broncos.
The grounds included in the harness are fine for just that Bletch. The harness functions. But what Attac was saying is what happens when the body is not a good grounding point for the harness.
YOU have to supply the base ground components such as the negative battery cable and every other kind of ground jumper to "bond" the body panels together. The harness then uses what you've laid out as your basic platform, and runs from there.
So what you have to make sure to do is to cover the basics.
Your battery cables should be larger than stock. I use at least 4ga as a minimum, but more often than not use 2ga.
Grounding straps for other aspects can be as small as 10ga wire, but those little store-bought braided straps are handy, clean (look factory because they are) and are the equivalent of a heavy gauge wire.
So, with that in mind:
1. Good heavy gauge ground cable from the battery to the engine. Anywhere on the main block is fine (not the intake manifold or accessory bolt if you can avoid them) but closer to the starter motor is better.
2. A 10ga wire, or braided strap from the battery negative to the body. Usually the first point of contact is the passenger wheel well. That's where Ford put the one and only body ground originally, but you're going to add more.
3. Back of engine to firewall. Another wire or braided strap here is your hero in avoiding future head-scratchers when firing up your electrical systems for the first time.
4. A 10ga wire between your dash board and the firewall. Often the opposite side of the same screw/bolt you used to ground the back of the engine.
In the overkill is just enough department:
5. A good heavy cable between the engine and frame.
6. A 10ga wire between the alternator housing and the engine block.
7. If your body is older and rustier, a short 10ga jumper between the body and the windshield frame will do your wipers wonders.
8. Bond the hood to the cowl with another one of those braided straps. Doesn't help anything but maybe an underhood light from an electrical standpoint, but it very well might keep your sanity in check by reducing radio noise.
I'm sure all the factories don't do it for their health or some obscure under-hood lamp.
None of those last ones are completely necessary, but you're not really going to lose any sleep over missing electrons if you do them either.
But you can certainly see a pattern of slight overkill, and see too where a nice roll of 10ga black wire and a few extra ring terminals will come in very handy in the near future.
Paul
