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

[autopar3000]

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?

 

[CFD244]

Following along

 

[Cashtastic]

I am no pro in auto or electrical; and I too, am going on my own journey with wiring.
That being said, make sure you have a safety in place from your new alt wire. A worst case scenario sort of thing; fuse/breaker/fuseable link. The latter may or may not have been with your original harness.
Ive done something similar on a valiant as what youve described youre going for, and the only real obstacle immidiately I noticed was making sure clean/new power goes to the goodies that used to be spliced off of the ammeter wire [wether you used it, kept it, changed it etc].
I believe I'm understanding your question and yes, isolating that wire the way you're thinking from your 'new power setup' and send a live 12v into the old 10awg/"P" connection on the bulkhead would work the way you're thinking.
Better? A matter of opinion.
I ended up doing the same as I worked through cleaning things up and inspecting on my dart; that I had already unhooked the factory ammeter in.
Just my 2cents

 

[RustyRatRod]

If you want the factory ammeter to work, then yes, you need it. If not, then you can run a large gauge wire (forgive me I cannot remember the correct size) from the alternator to the large stud on the starter relay. This will effectively render the ammeter useless, as it will not read correctly any longer.

I've thought about doing it to my car, but everything behind the cluster is in good shape and I have no melted connectors anywhere. THe only things I have added electrically are the electronig ignition and a decent stereo system....although it has no external amp, so no big draw there. My ammeter works great and all the wiring is in good condition. So I don't plan on modifying anything at this point.

 

[Bodyperson]

The factory system works great. Reduce the load to the bulkhead with the headlight relay conversion and you are golden. The alternator input will never overload the circuit, it just kind of floats along. The fuse block protects the corresponding circuits. Its the battery side that burns stuff up.

 

[RustyRatRod]

The factory system works great. Reduce the load to the bulkhead with the headlight relay conversion and you are golden. The alternator input will never overload the circuit, it just kind of floats along. The fuse block protects the corresponding circuits. Its the battery side that burns stuff up.

I forgot to add in my response, I did just that with @crackedback's headlight wiring kit. Money well spent.

 

[CFD244]

@crackedback also supplied an alternator wire around harness in either 6 or 8 gauge with appropriate overload protection. IIRC his recommendation was to leave the original 10 gauge alt. wire in place when installing the extra alternator cable.

 

[Mattax]

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

Alternator field wires

One a dual field alternator, would it still function the same if the two wires were swapped on the field connections?

www.forabodiesonly.com

Illustrations of how a remote shunted ammeter can be wired to show just battery charge and discharge.

Amp gauge shunt

Mattax thanks for your help. Your last diagram makes a lot of sense, the size of the shunt and the guage of wire should not be to hard to figure just by the amount of needle movement. What size shunt would you recommend would you recommend as a starting point using an factory amp guage that has...

www.forabodiesonly.com

Some other with auxilery fuse and relay box in the engine compartment.

Fusible link or not?

I am going to install a relay to power a fused distribution block to power things like the line-lock, the efi, distributor, ignition box. Since I can put appropriate fuses for each item, would be beneficial or detrimental to put a fusible link in the line to power the relay. If so, would you...

www.forabodiesonly.com

^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).

 

[Bodyperson]

I forgot to add in my response, I did just that with @crackedback's headlight wiring kit. Money well spent.

I ended up building my own headlight wiring kit. I would have loved to purchase it from crackedback but I guess that wasn't in the cards for me. I hope he is okay. I also ran a 6 gauge wire directly to the battery and 2 wire field alternator and an electronic VR and ignition. I also bypassed the bulkhead connector with the BAT. red wire. Fabbed up the Sunpro voltage into my rally dash. That is kind of cool. I want an idiot light too but aint figured that one out yet.

 

[autopar3000]

I am no pro in auto or electrical; and I too, am going on my own journey with wiring.
That being said, make sure you have a safety in place from your new alt wire. A worst case scenario sort of thing; fuse/breaker/fuseable link. The latter may or may not have been with your original harness.
Ive done something similar on a valiant as what youve described youre going for, and the only real obstacle immidiately I noticed was making sure clean/new power goes to the goodies that used to be spliced off of the ammeter wire [wether you used it, kept it, changed it etc].
I believe I'm understanding your question and yes, isolating that wire the way you're thinking from your 'new power setup' and send a live 12v into the old 10awg/"P" connection on the bulkhead would work the way you're thinking.
Better? A matter of opinion.
I ended up doing the same as I worked through cleaning things up and inspecting on my dart; that I had already unhooked the factory ammeter in.
Just my 2cents

Thanks for the reply. I included an image of the same relay box I'll be using. The new alternator wire will be the big wire into the relay box on the right, so power will go through the big PAL2 fuse, then to the battery from the large connection on the left. There will also be a connection from the battery to the factory starter relay. That's how the Rams and Daks were wired, but obviously no ammeter on those. I know if you want the ammeter to work then all the car's power needs to run through it. I gave up on that idea years ago when I ran a shunt from the alternator to the battery, and I just run a separate volt meter.

With the new relay box I would still have to get power to inside the car, so that's why I was thinking to run a wire from the left terminal below to the bulkhead terminal that is normally the alternator charge wire. Thanks for confirming (to the best of your understanding) that it will work. Now... do I need to run a wire from the bulkhead terminal that normally has the fusible link and goes to the starter relay? If I don't care about the ammeter function then I don't see why it's required.

 

[autopar3000]

If you want the factory ammeter to work, then yes, you need it. If not, then you can run a large gauge wire (forgive me I cannot remember the correct size) from the alternator to the large stud on the starter relay. This will effectively render the ammeter useless, as it will not read correctly any longer.

I've thought about doing it to my car, but everything behind the cluster is in good shape and I have no melted connectors anywhere. THe only things I have added electrically are the electronig ignition and a decent stereo system....although it has no external amp, so no big draw there. My ammeter works great and all the wiring is in good condition. So I don't plan on modifying anything at this point.

Thanks Rusty. Adding that wire is exactly what I did when I put in the EFI to begin with. I figured a constantly running electric fuel pump was never part of Ma Mopar's plan, and it would put too much stress on the bulkhead connector and ammeter. Of course the ammeter no longer does ammeter things, but I'm OK with that and just run a volt meter.

Before EFI I had the exact same setup as you; just a simple stereo and electronic ignition, no melted wires and everything in good condition.

 

[autopar3000]

@crackedback also supplied an alternator wire around harness in either 6 or 8 gauge with appropriate overload protection. IIRC his recommendation was to leave the original 10 gauge alt. wire in place when installing the extra alternator cable.

Right... that was my initial thought. Just leave the original alternator wire into the bulkhead. But then I started asking myself why it needs to come from the alternator? In the factory setup the power goes from the alternator, into the bulkhead, through the ammeter, then out of the bulkhead to the starter relay. The first place that circuit sees a fuse is the fusible link coming out of the bulkhead.

So I was thinking why not send power from my relay box to that bulkhead terminal, rather than from the alternator? I could put that whole circuit through a fuse from the start.

 

[autopar3000]

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.

Hey Mattax, this is some quality advice for sure. I'm good an imagining and conceptualizing these things, but it would help to put a wiring diagram on paper and see it. Still just conceptualizing, here's what I'm thinking about the electrical equipment and the power for each:

Headlights, fuel pump, starter relay power, and EFI system will be powered from the relay box. Relay box connected to the alternator and battery.

Interior lights, side markers, taillights, radio, cigarette lighter (i.e. phone charger), and starter relay trigger powered from the connection that goes into the bulkhead terminal.


So there will be a lot less power going to the bulkhead terminal.

I'll go through those other links you posted when I'm not on the clock at work.

Thanks!

 

[autopar3000]

I could put that whole circuit through a fuse from the start.

The more I think about it, the more I start to believe this is irrelevant. As long as there's a fuse somewhere in the circuit the entire circuit is protected, right? (Not asking myself, asking anyone). Is there a benefit to having the fuse closer to the battery?

 

[autopar3000]

I ended up building my own headlight wiring kit. I would have loved to purchase it from crackedback but I guess that wasn't in the cards for me. I hope he is okay. I also ran a 6 gauge wire directly to the battery and 2 wire field alternator and an electronic VR and ignition. I also bypassed the bulkhead connector with the BAT. red wire. Fabbed up the Sunpro voltage into my rally dash. That is kind of cool. I want an idiot light too but aint figured that one out yet.

Can you tell me more about putting the Sunpro voltage meter into the rallye dash? I also have a rallye dash and will be pulling the bezel off soon, so this is a good time for me to do that kind of mod.

 

[Bodyperson]

Can you tell me more about putting the Sunpro voltage meter into the rallye dash? I also have a rallye dash and will be pulling the bezel off soon, so this is a good time for me to do that kind of mod.

Do a search for "Sunpro" couple different ways of doing it. I just gutted a spare amp gauge housing, disassemble the volt meter and it bolted right in. I had to drill new holes for the voltmeter. Getting those holes in the correct spot was the hardest part.

 

[Mattax]

I know if you want the ammeter to work then all the car's power needs to run through it.

A falacy [sp?]
Ammeters only show battery discharge and charging. That's the only power that goes through them.

But then I started asking myself why it needs to come from the alternator? In the factory setup the power goes from the alternator, into the bulkhead, through the ammeter, then out of the bulkhead to the starter relay.

Because it doesn't. The alternator directly feeds the main circuits that branch off from the main splice. (up through '74 models)

I'll go through those other links you posted when I'm not on the clock at work.

I hear you! One reason I'm not on the forum as much as in the past.
When you look at those links, the diagrams should help clarify what I posted above about the power feeds.

Hey Mattax, this is some quality advice for sure. I'm good an imagining and conceptualizing these things, but it would help to put a wiring diagram on paper and see it. Still just conceptualizing, here's what I'm thinking about the electrical equipment and the power for each:

Me too

As long as there's a fuse somewhere in the circuit the entire circuit is protected, right?

A fuse protects against overloads including shorts after the fuse.
A short to ground before the fuse will continue to short.
- When it comes to the alternator, in most cases the short will stop it from functioning.
-- If the short kills power to the ignition, the engine stops turning and the alternator stops generating electricity
-- If the short kills power to the field, the field dies and the alternator stops producing electricity.

The fusible link was implemented to reduce the danger from the battery. If battery positive shorts to ground, it will continue to supply power until the connection burns out or it runs out of energy. A 16 gage fusible link will melt before the 12 gage wires. That's the concept anyway.

 

[autopar3000]

Do a search for "Sunpro" couple different ways of doing it. I just gutted a spare amp gauge housing, disassemble the volt meter and it bolted right in. I had to drill new holes for the voltmeter. Getting those holes in the correct spot was the hardest part.

View attachment 1716204761

View attachment 1716204762

Oh man, that is awesome. I'm definitely doing something similar.

 

[autopar3000]

OK, so I broke down and created that diagram Mattax suggested. I used his diagram as a starting point to show what I'm considering. Thoughts?

 

[Mattax]

Right. Good. Helps me too.
A couple comments
There needs to be a route to the key switch with power. Or to put it another way, the feed to the key switch has to be hot at all times.
So thats a line the should have a fusible link or maxi-fuse.

I don't know what 1, 2, 3 represent but I would think any circuit on a relay can be fused or have a circuit breaker.

What pulls 120 amps!? Is there a winch? I would think that would be a big wire, like a starter cable 6, 4, or 2 gage.

And drawing note: On a 1970 the J1 wire feeding the ignition switch will be 12 gage red. I drew it as a black feed because one year in the early or mid 1960s the shop manual shows it black.

 

[Mattax]

In the arrangement shown below the number of junctions and fuses power from the alternator has to flow through has been minimized.
On the other hand, if you were using the battery to soak up some of the electrical noise, then the alternator output should be attached to the battery positive. In which case you ahve to put a link or maxifuse on the line.

Obviuously the relays will need trigger wires. For examplem EFI and fuel pump needs to be triggered by the ignition start and the ignition run circuits, etc.

Note: Wire H1 is the power for the horn. It goes to the horn relay. No fuse on that until '73.

 

[autopar3000]

Thanks Mattax! I'll start with this, because I should have explained it:

I don't know what 1, 2, 3 represent but I would think any circuit on a relay can be fused or have a circuit breaker.

What pulls 120 amps!? Is there a winch? I would think that would be a big wire, like a starter cable 6, 4, or 2 gage.

1, 2, and 3 are PAL fuses, which are essentially fusible links. The #1 is the main fuse between the alternator and the battery that you can see in the image of the relay box in post #10. Ha ha, hopefully nothing pulls 120 amps! The wires on either side of that 120 amp fuse are really big, probably 2 gauge or bigger. 120 amps might have been OK for a 2nd gen Ram, but it makes sense for the old Swinger so I'll replace that with something smaller, probably 80 amps. Numbers 2 and 3 will be one of the other fuses in the relay box.

There needs to be a route to the key switch with power. Or to put it another way, the feed to the key switch has to be hot at all times.
So thats a line the should have a fusible link or maxi-fuse.

Right, that's the wire that's using fuse #2. It would be coming from the relay box (which is also a power distribution unit) and hot at all times. I would run it through a fuse, not sure of the size but it only needs to power the interior lights, side markers, taillights, radio, cigarette lighter, and starter relay trigger. I was thinking 30 amps.

The wire on fuse #3 is from the relay box to the starter relay. As you know, the factory setup would have the starter relay connected to the power cable coming out of the bulkhead. The starter relay fuse on the Ram was 40 amps, but I will probably start with a 30 and see how that goes.

The more questions you ask and the more I explain it, the more I think it will work. The only thing I'm not 100% sure about is whether I need a power connection coming out from the bulkhead to the starter relay (or to the relay box, since I'm already powering the starter relay via the relay box). Is it also required to power the ignition switch, along with the wire on fuse #2? Maybe I'll wire it in regardless.

 

[autopar3000]

In the arrangement shown below the number of junctions and fuses power from the alternator has to flow through has been minimized.
On the other hand, if you were using the battery to soak up some of the electrical noise, then the alternator output should be attached to the battery positive. In which case you ahve to put a link or maxifuse on the line.

View attachment 1716204878

Obviuously the relays will need trigger wires. For examplem EFI and fuel pump needs to be triggered by the ignition start and the ignition run circuits, etc.

Note: Wire H1 is the power for the horn. It goes to the horn relay. No fuse on that until '73.

YES!! This is pretty much the design! Still, the only question is if the power coming out of the bulkhead is even necessary. I think I'll stop thinking about it and just do it anyway.

Good point about the horn not having a fuse... that power wire is running right under my relay box so I might run the wire through the spare ATO fuse slot.

Thanks so much for your help with this, and thanks to the others that helped as well. FABO is hands down the best forum on the interwebs, and it's the people that make it that way.

 

[Mattax]

Whether you use the factory muticonnector on the bulkhead or a grommet is up to you. More important is good support without strain. Connectors also are good locations for test probes.
There must be a route into and out of the passenger compartment. Power has to get to the key switch.

For example, with the key in start, current can flow through the ignition start (J3) and the starter relay wire (S1).
Assuming the neutral safety is grounding, current from S1 flows through the relay's electromagnet to ground.
In your case J3 needs to go to whatever ignition and EFI relay is in the Dakota harness.

Dome light, Parking Lights, hazards all got power from the 'always hot' buss in the fuse box.
Wipers, turn signals, radio get power from the 'accessory' feed off of the key switch. Some are fused, the wipers have circuit breaker - usually in the wiper switch.

Hopefully that makes sense as to why there must be a power wire going into the passenger compartment, and at least a few coming back out. With relays the electrical load will be less for those just being used as triggers.

 

[CFD244]

Great thread.