Power and ground distribution when wiring

These two drawings represent what I believe is two methods to wire the dash gauges. The top is by running a jumper from gauge to gauge...the bottom is by having an independent wire from each gauge to the bus bar.

My questions are, is one of these methods electrically superior to the other and should I consider a different method?

 

In high power situations (things that draw a lot of amps) I'd say that drawing number 2 would be desirable. The idea with drawing 2 is to reduce voltage drop caused by wires that are normally smaller than the buss bar.

The situation with gauges is different. The gauges and their associated sensors are (usually) very low power so the hook up in drawing 1 would work fine. BUT gauges aren't normally hooked up like that. About the only situation where they would be hooked up that way is for illumination. The sensors can be a plus voltage or a ground depending on the sensor but in either case you could daisy chain your plus voltage or grounds as required by the gauge and sensor. Drawing 2 would be good for something like driving lights.

There are a lot of variables here and to make a short answer long we could discuss Ohm's Law.....

 

I was thinking about using option 1 separately for the dash lights, gauges, and switches (essentially 3 daisy chains that are separate from each other).

 

I agree - for automotive wiring, the advantage of a star ground (or power) is negligible. Daisy chain them. The quality of your connections is way more important than the ground paths.

In sensitive applications (ie high frequency, low noise), star grounds are superior.

 

Just to make sure we're speaking the same language, this is what I have in mind...acceptable for this application?

FYI, this is for Autometer Sport Comp.

 

When I built the harness for my 62, I ran individual power leads to each gauge in the dash and grounded them all off a common ground. A variation of both drawings.

 

This is a little puzzling, since you don't show the senders in the circuits anywhere. If they are mechanical gauges, then all they need from the wiring is lighting connections. Electrical gauges need some remote sender in the power circuit somewhere. Oil pressure, for example, is grounded through the oil pressure sending unit.

But generally, if you need a separate ground or power feed, you can wire it however is most convenient. Do you understand the difference between daisy chain and star? Star has a separate wire for each ground, going to a single ground point. Daisy chain connects each ground in series with one wire, then to the single ground. In sensitive circuits, you try to avoid daisy chaining because it can lead to ground loops: unintended circuits due to the voltage drops along the ground chain, and inductive/capacitive coupling. But those effects are vanishingly small in DC automotive wiring. Just wire it up so that the connections are neat and correct. Daisy chains are convenient, and fine for this application.

 

These are electrical gauges, not mechanical. The instructions for the gauge indicate a power lead, ground lead, and a sensor lead in addition to the lighting circuit. I'm not showing the sensor lead in the diagram because I assume that the sensor itself is grounded where it is installed, i.e. through the threads etc. or in the case of the fuel sender grounded to the body.

The above diagram was supposed to show a daisy chain where a jumper wire would go from gauge to gauge and finally end at a termination point...instead of from guage to termination point for each guage (the star?)

I also intended to keep gauge power and ground separate from light power and ground as well as switch power and ground, i.e. 3 separate daisy chains, to help keep the electrical gremlins away.

 

On my 3B where I did all of the wiring, everything is grounded back to the battery with all instrumentation having its own ground wire. I don't think it will make much difference in your case, but like Tim noted, make sure the connections are good-multiple opportunities to cause problems.