Mattax, thank you for the reply.

"Not sure what you mean here. The positive cable should have a very wire (4 gage or 2 ga) to the starter and a somewhat heavy wire to the stud on the starter relay. A 10 gauge fusible link is a larger wire than many cars came for the battery feed. Its going to take a lot of amps to melt that! If you go that large, I'd suggest looking for a protective insulating shield for the relay. Stock on many models but get lost."

On my '73 truck, the Red, positive battery cable runs from the pos battery post to a lug on the starter relay, and then a similar sized cable runs from relay to the starter. So on your diagram, I just saw a FL going from battery pos post to a termial block, and from there, a wire to the starter relay.

From looking at your diagrams and Nacho's work, I was looking at just running one RED wire from amp gauge stud to the starter relay, with a FL in it before the starter relay. Then keep the same heavy battery cable I already have in place from the starter relay to the pos battery post.

I have a FSM for the truck, as well as a stand-alone wiring diagram; I'll look at it today to see if it offered an alternative routing, like you have shown.

"The terminal block with the arrow pointing to it would be a reasonable location to add an auxilery fuse or breaker box. But, if the loads you will be adding will be in the passenger compartment (and not using relays), then the factory bulkhead connecting terminals may be too small for the alternator output.This where an exact diagram for your rig would be really helpful. Or maybe its obvious when you look at the firewall. For example,in A-bodies around '75 and certainly in '76, the alternator output had a welded splice junction on the engine side which split the power before going through the bulkhead connector. The same concept might have been introduced earlier on intermediates, full size or trucks.The '73 Dart optional wiring is a little simpler to implement, and you could add a terminal block anywere in the alternator line."

Just looking at the engine bay, not sure if the line from the alternator splits off that welded splice on the engine side or not, but I'll will check it out. At any rate, I think I will work out placing an auxilliary power terminal with the feed coming off the alternator stud. Anything I'd run on that (USB power port, extra lights, CB) WILL be fused. Not planning on putting the wrecker boom/winch back on the truck, and no plans to add a winch, but if I did, I'll power it from the battery.

It also sounds, from all the reading I've been doing, like it's not a bad idea to put in a higher output alternator. The one on it is stock. Even with crackedback's headlight relay added on, the headlights dim at idle.

On my '73 truck, the Red, positive battery cable runs from the pos battery post to a lug on the starter relay, and then a similar sized cable runs from relay to the starter.
Maybe it has a remote starter solenoid relay.
I think Chrysler used them late 50s early 60s for cars. Ford and at least some AMC/Jeeps used them in the 70s and 80s. Actually some of the last years of the SJ Jeeps had both a Chrysler type starter relay and the Ford type starter solenoid - maybe around 89 - 90. I think 91 it got different starter with an internal solenoid like our cars have.


I have a FSM for the truck, as well as a stand-alone wiring diagram; I'll look at it today to see if it offered an alternative routing, like you have shown.
if you can also take some photos and post (or e-mail), that would be super.

I doubt the USB or CB is a huge power draw. Lights are pretty big draw. I don't know about the wrecker type winches. I drove a rusty '87 Dodge with mason's dump and plow - gummeymint work truck that got little love - and IIRC power connections for them were at the battery. The two radio - I don't know where it was tied in. Didn't matter. It was only turned on when the truck was running. Only point is that truck survived 15 years, and there was a near identical one a nearby town owned. Same age, more rust, different color - maybe no 2 way radio. LOL.

It also sounds, from all the reading I've been doing, like it's not a bad idea to put in a higher output alternator. The one on it is stock. Even with crackedback's headlight relay added on, the headlights dim at idle.
Well this becomes a difficult subject.
Sniper has posted that his all original car does not dim its headlights.
I don't know if its the lamps on the car draw less, the wiring is in better shape, or the alternator is an original with matching rotor and stator.
But many folks do see that, and not surprising, the ammeter showing slight discharge - especially with turn signals on and foot on the brake (stop lights on).

All alternators produce less power at low rpms.
Many 'rebuilt' and 'remanufactured' alternators no longer have the original stator and rotor - so they may be a mismatched set. They work, but prob not as efficient, which shows up most at low rpm.
Some 'high output' alternators produce more power at low rpms than stock, and many do not.
I think sometimes we shoot ourselves in the foot because the 'high output' alternator was made by installing a rotor that has higher current draw. So sure it produces a stronger electomagnetic field, but it sucks more juice to do so. So depending on idle speed, it may use more current than it produces. Also if the regulator can't handle the higher current draw, it will fail sooner.

My only suggestion is to shop carefully to be sure you get one that has better output at idle than the one you already own.
I *think* some of the high output alternators Chrysler installed were a different design and manufacture. For example there's some 60's service bulletins in Hamtramck-Historical showing a Leece-neville alternator which used had wiring to the regulator similar to shown in the '73 optional diagrams.

If you decide to go NOS gauges, here's a good price on O/P. NOT mine.

https://www.ebay.com/itm/72-77-dodge-pick-up-truck-nos-oil-pressure-gauge-3635176/264508064991?

Ran across this.
https://web.archive.org/web/20180711165857/http://dave78chieftain.com/Ignition_Syste.html
At the bottom is a nicely done diagram of '73 and '74 wiring.
The original pages still exist but the archived version's images are easier to see thanks to P-Bucket
http://dave78chieftain.com/Ignition_Syste.html
It shows that motorhomes in '74 got a remote shunt ammeter, and the main feeds from the alternator and the battery join in the engine compartment. Then the power through the firewall is split, one wire going to the key switch, the other to the circuits that are always hot.

Thanks for finding that. My FSM shows the full blown system, with no separate diagrams really, for each area of the vehicle. Makes it a little harder to work through, to me. I bought a blown-up version, with some color coding to it, from Classic Car Wiring.

Won't be able to get into this till after the weekend. Who is a good vendor for things like the FL wire, good crimp connectors and a good set of crimpers? Still have cleanup on the dash and gauge cluster to do, testing the oil, temp, and fuel gauges, and repainting the needles

Somebody suggested that Marine quality items/wiring are the way to go along with good crimping/soldering/shrink wrap tubing

Those diagrams I posted are created using the factory diagrams. Rarely did they provide schematics and even rarer were harness layouts in the FSMs.
It's up to us (the Techs) to use the factory diagram to make what we need.
http://www.imperialclub.com/Repair/Lit/Master/247/index.htm

I do about half on paper but easiest to post up the ones I've done the computer using MS Paint and IRFAN.

I'm one of those who likes marine grade wire. Can usually walk in and buy by the foot - if there's a marine supply in the area. Most parts stores carry automotive wire with GP (General Purpose) insulation. It's OK. But for high heat or locations where they may get covered in oil, there are better grades for that purpose.
Crimpers - Well a couple years ago I went full into using factory type connectors. Packard 58 and Packard 56 which use 'open barrel' crimps on the wire and another on the insulation.
For the most the Astro crimper with changable jaws has been pretty good. For some of the male terminals the jaw is too wide. I know a couple people who have ground the jaws. I ended up buying yet another crimper from American Wire (a copy of the Packard electric crimpers).
For heavier loads, ring terminals are good or connector that has more contact area than the Packard 58/56.

For factory wires colors may have to go to a place like Rhode Island Wire. Fusible link is pretty readily available. For links with Chrysler colors I've seen some places selling those, just can't recall who off hand.

Nice work on those diagrams, and thanks for posting them out there!

Looking through both the FSM and the Classic Car Wiring diagrams, the welded splice off the alternator feed is made on the cab side of the bulkhead connector. On the DodgeCharger.com forum thread, it looks like user PocketThunder's Charger is the same way; the welded splice is on the inside of the vehicle. If I'm reading his posts correctly, he cut and capped the original alternator feed wire on the engine side of the firewall, where it would have gone INTO the bulkhead connector. He also capped off the other side of the original feed inside the car under the dash where come OFF the bulkhead connector. He left the other end of this wire ON the amp gauge where it was always connected. Along with it is his new Alternator wire to the amp gauge, both of those on the same post. If I see this correctly, in this way, he has power to his key switch, light switch, and fuse box, because the new alternator wire is now connected to whats left of the old alternator wire on the "black wire" post of the amp gauge. Am I seeing that correctly? Is that a good idea if the original alternator wire bulkhead connectors are not safe to leave in place?

On your diagrams, Mattax, I'm guessing that the FL on the alternator side that I see there are for instances when something screws up with the alternator, such as with the "fried harness wires. Why??" thead??

Yes. That's the norm on the older cars. A welded splice inside that acts as the power distribution point.
I just wanted to be sure that's what your truck had.



I think you are interpreting it correctly.
I don't see any particular advantage or disadvantage to leaving the original alternator output wire vs. removing it. And if it is removed, I think leaving the original segment to the connector is pretty safe. But if you wanted to remove it and tape it, you could do that too. I'd wrap it up against the harness so it didn't flop around.

[img]http://www.dodgecharger.com/forum/index.php?PHPSESSID=feg5ibvs5qqmhsv7qgkli8n8c2&action=dlattach;topic=33574.0;attach=264330;image[/img]


Which diagram are you looking at? The optional wiring ones earlier in thead?

And yes, alternator internally grounding failure occassionally happens. Also sometime a wrench touches the exposed alternator batt terminal while the battery is hooked up. Actually should be a insulating partial cover over it - but many cars no longer have them.

If the output terminal gets loose, or the insulating washers fail, then the battery can short to the housings.
Same if any part of the positive rectifier touches ground.
Some of theguys who know more about electronic tech may be able to say whether diode can fail in way that would let through high current (in the wrong direction). I pretty sure they sometimes can slowly 'leak' in reverse when they fail.

"Which diagram are you looking at? The optional wiring ones earlier in thread?" Yes, those are the ones. I'll take the firewall plug apart and look the alternator feed connections over this week. If they are in good shape, I'll give as good a cleaning as possible, pack it with dielectric grease, re-connect, and leave it in use, along with a new wire on that side coming in through a grommet. Will be replacing the red wire.

Can't wait to get the dash back together and see how it looks with the new LED's.

Again, thanks, to all, for the time and knowledge/experience. As I get this back together, I will try to post how I did it, with pics, and how well it does.

OK. Lets see if this works.

On the A-body version, there's just one fusible link. It can protects all the wiring downstream that is 16 gage or larger. In other words, it should melt before the 10, 12, and even the 14 gage wires on the ignition circuit.



On the B-body version, the green 10 gage fusible link should melt before the 6 or 8 gage wires leading to the alternator.
A blue 16 gage FL protects the standard 10, 12, and 14 gage wires.

A couple of follow up observations.
With the 65 amp B-body wiring, it becomes tricky to run parallel wires from the alternator to the main splice. If we run a FL on each, then we main not be adaquitely be protecting the smaller wires.

16 ga FL ---10 ga ----12 ga----Welded---12 ga---Fusebox
16 ga FL ---10 ga ----12 ga----Junction---12 ga ---switch ---14 ga ----

Now lets say that 14 ga wire rubs on some metal and ground out.
Power from the battery can flow through both fusible links. Sure it will take the shortest route first, but as resistance increases, it will find the next easiest path.


I noticed the Q3 label on my diagram didn't make sense (accessories are switched)so I went back to the service manual to see what it should be - fusebox. Duh!

While looking at the FSM, I noticed there was also a 60 amp wiring option for the b-bodies with a more practical wire sizes to work with.\
Be interesting to see whether it ends up more like the A-body 60 amp or B-body 65 amp wiring.
It looks like the 65 amp was a special leece neville unit. Someone may know more about that.

Thank you. I'll study some more on my FSM diagram tomorrow. Thanks for telling me how those wire code designations work; starting to make more sense to me now. I thought a route code of some type for each wire length.

FWIW the 60 amp B-body option has same layout or concept as the 65 amp option.
But it only uses one extra terminal and has smaller, more reasonably sized wires and links.
Here's the quickest version I could do.

If I DID end up replacing the alternator, and went up to an 80 or 85 amp version, will the 10 gauge wire still be fine? I've no need for anything bigger on alternators in this rig.

This is what Nacho was talking about. It doesn't really matter what the maximum the alternator is capable of.
When sizing wires the question is how much power the lights or equipment will draw?
Then the fuse is selected to never open under normal current draw, but to melt well before the smallest wire would melt if grounded.

The other thing about the alternator is that it will stop producing power if there is short to ground in the system. If current is shorting to ground, its no longer flowing to the rotor and so the magnetic field collapses. Result is no power.

Lets look at the 60 amp Dart wiring. It originally showed that with extra equipment on the alternator side of the ammeter. IIRC its the rear window electric defroster. So that can draw a bunch of current. Therefore its probable the optional wiring arrangement was designed to support that extra current. Notice they left the standard 16 gage fusible link.

The battery recharging is the only device that is difficult to plan for. At least I think so.
The amount of current it will draw depends on how much its depleted as well as the supply current.
On the stock alternators, the alternator power at idle was a limiting factor which helped keep the battery from charging too rapidly.
Now IF this new 85 amp alternator can produce 45 amps at 14 Volts while idling, and the battery is low, this is when the larger wires will stay cooler.
5 amps will go to running the ignition and supplying the field, and the other 40 amps will go to the battery for recharging.
As the battery gets recharged, it will draw less and less current even when supplied with power at 14 Volts.

But if the engine is running and the battery is only being used for starting (and maybe to help a little at stop lights with lights, wipers, A/C) then I would think you could stay with the 16 gage fusible link in he battery feed. As a 16 gage FL would protect the system as well as stock, then a second one coming off the terminal block would not be needed.

Mattax, I'm leaning towards taking it all out of the bulkhead connectors. In your last diagram, any reason I can't come on from the 12 gauge wire on the cab side, where the splice goes to the ignition, lights, and fuse box, and splice in a length of additional 12 gauge black wire through the grommet at the firewall, to the engine bay? Your diagram has the 8 gauge from the alt hitting a terminal stud, where 10 gauge goes to a 16 gauge FL, to 10 gauge, to the bulkhead connector, to that 12 gauge on the cab side. Can I just carry 12 gauge through the grommet, straight into the 16 gauge FL? Can the 14 gauge FL connect straight to that terminal stud? or is there a reason 10 gauge wire comes off it, and then into the FL?

I'm planning on doing this per that last diagram, as it matches very well with the truck's setup. I'm going to unwrap all the loom needed to get the original wires being eliminated OUT of the loom, and re-wrap new wires in where positioned, with the cloth loom tape and/or the split loom sleeving. Got everything ordered but the actual connectors.

Thanks!

Mattax, this is what I was thinking of. I have the harness unwrapped under the dash to get the wire from the welded splice to the amp gauge cut and taped off, and the wire from the cab side of bulkhead to where I can splice new 12 gauge bl wire from where I cut off the bulkhead connector. Feed that newly spliced 12 gauge bl wire through the same new firewall grommet as the 2 new amp gauge wires. Run it to the new 16 gauge FL, which goes to the terminal block on the alternator feed line.

Meant to ask; what can I use to remove the connectors in the bulkhead blocks? I want to remove both black and red wire completely from the bulkhead blocks.

Thanks,

Joe