Do I really need the wire from the alternator to the bulkhead connector?

autopar3000 said
This question is for the guys that like wiring and electrical challenges, if those type of people actually exist .

I have a 5.9 Magnum running the factory EFI and 46rh transmission in my 70 Dart, and it’s awesome (for me). It all works really well but when I initially did everything a couple years ago I didn’t use an ASD relay, and I didn’t leave provisions for cruise control or AC (for those that aren’t familiar, the ASD relay powers the coil and fuel injectors). However, since I added an electric fuel pump I did run a 10 AWG wire from the alternator to the battery positive (with a 50 amp fuse) to take the pressure off the bulkhead connections.

Now I’m working to fix the things I did wrong, add cruise, set myself up for AC one day, and put the headlights on relays. So I’m redoing the wiring and putting in an engine bay fuse / relay box from a 1994 Ram. The relay box will house the headlights relays, fuel pump relay, and the ASD relay. I will still be using the factory style starting system, including the factory starter relay and NSS control.

Just like a 90s Ram or Dakota, I will be running a huge charge cable from the alternator to the relay box terminal, which then goes through a 120 amp PAL fuse, and finally to battery positive (I will probably replace that 120 with a 100 or 80 amp fuse).

I was initially planning to also include the charge cable from the alternator to the bulkhead connector, just like a factory setup, but now I’m questioning that idea. I wonder if it would be better to only have the charge cable from the alternator to the relay box, then have a wire (probably 10 AWG) from the relay box to the bulkhead. If I understand it correctly, this would provide the power to everything inside the car except for those things I mentioned I’m putting on relays. And again, if I understand it correctly, I would not need the wire with the fusible link that goes from the bulkhead connector out to the factory starter relay. Instead, I would add a connection from the relay box to the start relay (fused, of course).

What do you guys think? Should I forget about the usual charge cable from the alternator to the bulkhead, and instead run the power to the bulkhead from the relay box? If so, does that mean I can forget about the power cable with the fusible link that goes from the bulkhead to the starter relay?

You have a custom setup. You need to come up with a wiring strategy for supplying power and distributing it to the electrical equipment. Make list of the power needs for each of the items. Some will be variable, so for those list the range. Then make drawing of how the electricity will get from the power supply to the distribution point for various circuits.

Using the maximum loads you can figure out the wire sizes needed, and the protection for the wires.

Plenty of posts explaining how the factory did it on your '70, as well as some factory options that worked using the same strategic approach. Your setup has very different needs and does not readily adapt to that strategy. If you want an ammeter to monitor battery charging, it can be done with a remote shunted ammeter (available from aircraft supply) but there must be one path on the final leg to the battery.

Connecting the power (alternator and battery outputs) to main circuits - factory scheme

Adding constant loads with a factory scheme
https://www.forabodiesonly.com/mopar/threads/alternator-field-wires.459766/post-1972923668
Illustrations of how a remote shunted ammeter can be wired to show just battery charge and discharge.
https://www.forabodiesonly.com/mopar/threads/amp-gauge-shunt.425145/post-1972353688
Some other with auxilery fuse and relay box in the engine compartment.
https://www.forabodiesonly.com/mopar/threads/fusible-link-or-not.458737/#post-1972904806^I'm not suggesting this, or any of the other schemes that use an ammeter.^
That's up to you. These are examples to help you understand the concepts of so you can develop your own strategy for this car.

The fusible links (or maxi-fuse) in a main feed is to protect against the battery shorting to ground. Each one is a restriction. With the tradition wiring arrangements only one was needed because there was only one connection from the battery to the other circuits (starter connections were unprotected).