Melting Wires

[m_m70]

It looks like one end of that wire hooked to the block and the other hooked to the starter relay terminal? If so you created a direct short connecting a positive (+) to ground (-). That would do it.

this is what I see as well........

 

[71 CA Bronco]

Hey Blue where are you located. Maybe someone on here can give you a hand figuring this out? An extra set of eyes can come in handy at times.

 

[DirtDonk]

There is no engine-to-body ground on a Bronco in the factory harness. That is except the tiny little 20ga or so wire between the alternator and the regulator. It's buried in the harness from the alternator and only shows up near the regulator where it's attached at the mounting screw.
There "should have been" a ground between the back of the engine and the firewall to bond the body and engine together and get a better ground to the dash board area, but Ford never saw fit to put one in Early Broncos like they did other vehicles.

The only large gauge Black wire in an Early Bronco is the main power loop wire. It's Black at the starter relay and Black w/yellow at the alternator on most years. Some later years used Black w/red at the battery end, and some very early ones did not get the yellow stripe at the alternator for some reason. But generally speaking, your '69 would have had a yellow stripe over much of it's run from the alternator into the cabin.
The ammeter is the only real reason for this wire to be so routed. Most other vehicles ran the charge wire straight from the BAT terminal of the alternator over to the battery positive (usually at the starter relay for convenience and probably cost). With the ammeter telling the driver what current is being drained or output to charge the battery, the charge wire has to run through the entire harness basically. Starts at the back of the alternator, runs up to the firewall connector, over to the ammeter (where there is another connector), back out the other firewall connector and over to the starter relay.
When the engine is off, the battery sends power out over this wire to run the accessories. When the engine is running and the alternator charging, the flow of current reverses and the excess is used to re-charge the battery.

The circuit is very reliable normally, and has the protection of the fusible link. But if something happens to that wire and it short circuits, and the fusible link does not do it's job, you get a meltdown. Not sure why your link did not blow, but it happens. It looks to be still intact, but a closer inspection will reveal that.

When you look at the back of the alternator, you should see 3 wires:
1. An Orange wire (field) that runs from the FLD terminal straight up to the F terminal of the regulator.
2. A tiny Black wire, likely in the form of a small metal tab/ring on your strain relief that attaches to one of the GRD studs.
3. A large Black (possibly with yellow stripe) that runs from the BAT terminal up into the harness. This is the one that does all the work and looks like the one that had the melt-down.

There is no separate ground outside of the harness unless added by an owner. If that was indeed a ground, then the reason it melted was because too much current was passing through it for it's gauge size. The most common reason for that is a failed main engine ground cable from the battery to the block, OR a short circuit to a positive voltage source that's heavier duty than the wire that melted.
Possibly other stuff I'm missing, since I don't know all about all years, but those are the basics.

I've even seen some odd wiring setups on '68's and '69's, so I might be incorrect about separate grounds and such. Ford did change the main alternator harness strain relief (that large rubber molded thingy with the wires going into it and the two attaching rings in your pic) several times over the years. So I'm sure I have not seen every style used.
Looking forward to seeing yours in more detail.

Does the melted wire go into that molded connector/strain relief? Or is it separate?

Paul

 

[Blue1969]

this is what I see as well........

No, its between the mounting bracket of the starter relay and inner fender. It is not attached to any terminal on the starter relay.

 

[Blue1969]

Hey Blue where are you located. Maybe someone on here can give you a hand figuring this out? An extra set of eyes can come in handy at times.

I'm in Oakwood, GA (Lake Lanier)- 40 miles northeast of Atlanta

 

[Blue1969]

There is no engine-to-body ground on a Bronco in the factory harness. That is except the tiny little 20ga or so wire between the alternator and the regulator. It's buried in the harness from the alternator and only shows up near the regulator where it's attached at the mounting screw.
There "should have been" a ground between the back of the engine and the firewall to bond the body and engine together and get a better ground to the dash board area, but Ford never saw fit to put one in Early Broncos like they did other vehicles.

The only large gauge Black wire in an Early Bronco is the main power loop wire. It's Black at the starter relay and Black w/yellow at the alternator on most years. Some later years used Black w/red at the battery end, and some very early ones did not get the yellow stripe at the alternator for some reason. But generally speaking, your '69 would have had a yellow stripe over much of it's run from the alternator into the cabin.
The ammeter is the only real reason for this wire to be so routed. Most other vehicles ran the charge wire straight from the BAT terminal of the alternator over to the battery positive (usually at the starter relay for convenience and probably cost). With the ammeter telling the driver what current is being drained or output to charge the battery, the charge wire has to run through the entire harness basically. Starts at the back of the alternator, runs up to the firewall connector, over to the ammeter (where there is another connector), back out the other firewall connector and over to the starter relay.
When the engine is off, the battery sends power out over this wire to run the accessories. When the engine is running and the alternator charging, the flow of current reverses and the excess is used to re-charge the battery.

The circuit is very reliable normally, and has the protection of the fusible link. But if something happens to that wire and it short circuits, and the fusible link does not do it's job, you get a meltdown. Not sure why your link did not blow, but it happens. It looks to be still intact, but a closer inspection will reveal that.

Paul, where do I find this fusible link?

When you look at the back of the alternator, you should see 3 wires:
1. An Orange wire (field) that runs from the FLD terminal straight up to the F terminal of the regulator.
2. A tiny Black wire, likely in the form of a small metal tab/ring on your strain relief that attaches to one of the GRD studs.
3. A large Black (possibly with yellow stripe) that runs from the BAT terminal up into the harness. This is the one that does all the work and looks like the one that had the melt-down.

I'm going to take the alternator off and get a closer look at everything. It may be a day or so, and I'll get back with you. These short daylight hours is getting in the way of working on it. Thanks for your help Paul.

There is no separate ground outside of the harness unless added by an owner. If that was indeed a ground, then the reason it melted was because too much current was passing through it for it's gauge size. The most common reason for that is a failed main engine ground cable from the battery to the block, OR a short circuit to a positive voltage source that's heavier duty than the wire that melted.
Possibly other stuff I'm missing, since I don't know all about all years, but those are the basics.

I've even seen some odd wiring setups on '68's and '69's, so I might be incorrect about separate grounds and such. Ford did change the main alternator harness strain relief (that large rubber molded thingy with the wires going into it and the two attaching rings in your pic) several times over the years. So I'm sure I have not seen every style used.
Looking forward to seeing yours in more detail.

Does the melted wire go into that molded connector/strain relief? Or is it separate?

Paul

 

[Rustytruck]

Minimum important grounds on a Bronco. Battery negative to the Body on inner fender. Battery ground to engine Block. ground connection between the mounting screws of the starter relay and the mounting screws for the voltage regulator. inferior ground from the alternator to its mounting hardware. inferior ground for the taillights to the rear of the frame on the drivers side. pis poor ground through the steering coupler.
the front lights and turn signals ground to the grill or core support.
worthy grounds to add, frame to engine block. the engine block to the body shell at the firewall.
alternator case to the engine Block especially if you have a 3G alternator.
important to have clean steel under the voltage regulator and the starter solenoid. all grounds need to be bare at its attachment. good clean grounds are the Broncos life blood. weird things happen when you have poor grounds and the system seeks a new ground path to function.

 

[Broncobowsher]

The problem is you think it is a single wire is the only thing damaged. In reality it is the harness and all the wires inside that harness that are damaged. That main wire may have been the one that got super hot and started melting insulation but that melting insulation is not limited to that one wire. As it melted, it melted insulation on the wires that it is bundled with. Every wire in that harness is compromised now. They may not be failed, or shorted completely, but they are not what they were. As you (or someone else) takes the harness apart it will no longer be a bunch of seperate wires bundled into a harness. It is one blob of plastic from where the insulation of the seperate wire have fused into one. You have no idea if the wire seperation inside the blob is sound or not.

A rewire is really the correct thing to do. I can tell you are cringing at the thought/price of that. But really you are super lucky that the whole Bronco didn't burn to the ground. Because that is the typical result of an electrical fire like you experienced. Count your blessings you are not looking at a charred shell, be happy all you need to do is rewire the Bronco and not replace it.

FYI, if you have proper insurance this can be filed as a fire claim. You can have a shop fix it and just pay the deductable. Back in the 80's my parents had a car that had an electrical fire. Got super lucky (like you did) and the car didn't burn to the ground. And it was a repaired fire claim.

 

[Blue1969]

The problem is you think it is a single wire is the only thing damaged. In reality it is the harness and all the wires inside that harness that are damaged. That main wire may have been the one that got super hot and started melting insulation but that melting insulation is not limited to that one wire. As it melted, it melted insulation on the wires that it is bundled with. Every wire in that harness is compromised now. They may not be failed, or shorted completely, but they are not what they were. As you (or someone else) takes the harness apart it will no longer be a bunch of seperate wires bundled into a harness. It is one blob of plastic from where the insulation of the seperate wire have fused into one. You have no idea if the wire seperation inside the blob is sound or not.

I appreciate your insight. I'm going to take a closer look at everything, but I haven't really seen any blobs or melted insulation. I disconnected the battery as soon I could get stopped, probably 15 seconds from start to finish.

A rewire is really the correct thing to do. I can tell you are cringing at the thought/price of that. But really you are super lucky that the whole Bronco didn't burn to the ground. Because that is the typical result of an electrical fire like you experienced. Count your blessings you are not looking at a charred shell, be happy all you need to do is rewire the Bronco and not replace it.

You hit the nail on the head, I am cringing at the thought of a complete rewire. I'm not as knowledgeable about electricity as I wish I were, Another reason is one thing leads to another. If I do this, I might as well do that and it turns into a 2 year project.

FYI, if you have proper insurance this can be filed as a fire claim. You can have a shop fix it and just pay the deductable. Back in the 80's my parents had a car that had an electrical fire. Got super lucky (like you did) and the car didn't burn to the ground. And it was a repaired fire claim.

I haven't thought about insurance. I'll take a look at my policy. Any idea of a ballpark cost for a shop to replace the harness?

 

[Blue1969]

I unmounted the alternator to get a better look. The melted ground wire attached to the engine block did terminate under the starter relay. Would this be my engine to body ground from the factory? I believe what happened was the black and yellow charging wire shorted against the ground wire. i also believe the melted wire under the dash is the same wire although I can’t verify it’s color due to lack of visibility and condition of wire. i did notice the charging harness wasn‘t in great shape when I installed the new alternator. In fact,I taped up a couple of places on it. I guess I should’ve taken action then.

 

[DirtDonk]

Paul, where do I find this fusible link?

Look at the battery side of the starter relay. The Black wire has a molded-on ring terminal that I always thought was the fusible link itself, but more likely the first few inches of wire are the link. In your case there is also a small Yellow wire molded into it as it's used as a splice point too.
The Yellow wire should be the one to the voltage regulator's "A" terminal.

Fusible link wire looks like a larger gauge wire on the outside, but inside is a smaller version (4 gauges smaller I think?) that literally melts off when a wire is overloaded. It burns out before the rest of the wire has a chance to overheat. Basically a bit of sacrificial wire.

I unmounted the alternator to get a better look.

Got pics?

The melted ground wire attached to the engine block did terminate under the starter relay. Would this be my engine to body ground from the factory?

As mentioned, no such thing. At least I've never seen one.
Ford grounded the alternator through it's mounting bolt and case directly to the cylinder head. They also grounded the body with the main negative battery cable mid-way to the engine.
Maybe yours is different, but I'd say a ground like that was added by a PO. And it looks it too from here at least. But it's hard to tell because of it's poor condition.

On a typical Bronco wiring scheme, the only ground between the engine and the body is contained within the alternator harness and instead of mounting up at the starter relay it's mounted to the voltage regulator. This is an important little wire for the charging system.
The starter relay is normally grounded through it's screws to the body. The ground is usually lower down on the inner surface of the wheel well. Do you see a hole there facing the exhaust manifold about 2/3 of the way to the top of the wheel well?
I've seen one or two Broncos over the years that did not have this grounding point. But all the rest did have that in common.

Paul

 

[Blue1969]

Look at the battery side of the starter relay. The Black wire has a molded-on ring terminal that I always thought was the fusible link itself, but more likely the first few inches of wire are the link. In your case there is also a small Yellow wire molded into it as it's used as a splice point too.
The Yellow wire should be the one to the voltage regulator's "A" terminal.

Dead on Paul!

Fusible link wire looks like a larger gauge wire on the outside, but inside is a smaller version (4 gauges smaller I think?) that literally melts off when a wire is overloaded. It burns out before the rest of the wire has a chance to overheat. Basically a bit of sacrificial wire.

Got pics?

Black and yellow wire cooked on both sides of this junction. This wire above where the short occurred going to alternator looks unharmed. In other words, the short went in the other direction?

This is the other end of the wire from the engine, which was mounted under the relay bracket. Same thing, above where the short occurred, the wire looks unharmed, Do you think this ground to engine should have been connected elsewhere?

The ground wire connection is sketchy. I wish I could turn back the clock and address this wiring harness. I looked at on Tom's and should've went ahead and ordered it.

As mentioned, no such thing. At least I've never seen one.

Ford grounded the alternator through it's mounting bolt and case directly to the cylinder head. They also grounded the body with the main negative battery cable mid-way to the engine.
Maybe yours is different, but I'd say a ground like that was added by a PO. And it looks it too from here at least. But it's hard to tell because of it's poor condition.

On a typical Bronco wiring scheme, the only ground between the engine and the body is contained within the alternator harness and instead of mounting up at the starter relay it's mounted to the voltage regulator. This is an important little wire for the charging system.

Looks right, ground from alternator.

The starter relay is normally grounded through it's screws to the body. The ground is usually lower down on the inner surface of the wheel well. Do you see a hole there facing the exhaust manifold about 2/3 of the way to the top of the wheel well?

I forgot to check on this. I will at lunch.

I've seen one or two Broncos over the years that did not have this grounding point. But all the rest did have that in common.

Paul

 

[DirtDonk]

Fusible link looks like it's been fat and happy all this time. On vacation while Rome burned!

The ground is in fact your factory alternator-to-regulator ground. Looks like original end on the regulator side, but has been replaced at the alternator end. Does not appear that your ground shorted to your power. The ground is relatively intact and unless you see where it touched inside the harness (unlikely in this case) your problem came from somewhere else.

Note in your second pic you can clearly see the old original body ground hole in the sheet metal. You can even see the ghost image of the old metal tab.
By this time probably 95% of all EB's no longer have this original one because the battery cable was replaced with a standard cable. Owners don't always realize that what they think is just a mounting clamp, is in fact the ground. So they leave it out.
You should add back a body ground from your battery negative to the body metal. Either back to this same hole, or wherever it's more convenient. Usually people put it under one of the screws to the starter relay. But it's up to you.

Your original description had you removing the regulator and doing some painting. Painting is a good thing, but wherever you have a grounding need, it's a bad thing. So whenever you paint near a component's mounting point, make sure that the screws and the body and the hole are clean and free of rust and paint. Things that have to be grounded have to stay grounded.

I still think that what happened was when you disconnected the regulator from the body, if the battery was still hooked up then you fried the regulator. Then when you started the engine the alternator "full fielded" causing it to put out it's maximum total amperage the whole time it was capable of it. That would explain the instance of smoking wires only when you revved the engine up to accelerate. At idle the alternator is only putting out maybe 20 amps or so, but at higher rpm and with a tight belt, it can output it's max at least. Probably in the 55-65a range.
Normally this is not near enough to cause a problem. But if the original Black w/yellow wire was compromised in any way (extra resistance through corroded firewall connectors, or the ammeter connector for two examples) the wire could not handle 60a for an extended period and overheated to the melting point.

That's my guess at this point anyway. Until other clues crop up.

Paul

 

[Blue1969]

Fusible link looks like it's been fat and happy all this time. On vacation while Rome burned!

The ground is in fact your factory alternator-to-regulator ground. Looks like original end on the regulator side, but has been replaced at the alternator end. Does not appear that your ground shorted to your power. The ground is relatively intact and unless you see where it touched inside the harness (unlikely in this case) your problem came from somewhere else.

I'm referring to the ground wire that went to the engine and underneath the starter relay (the melted ground wire) as causing the short with the black/yellow wire, not the one from the alternator to the voltage regulator. Is that possible?

Note in your second pic you can clearly see the old original body ground hole in the sheet metal. You can even see the ghost image of the old metal tab.

Yes that's where I removed the relay, it was mounted there. I unscrewed it to get a better picture of the wiring. You can see where I cleaned the paint off.

By this time probably 95% of all EB's no longer have this original one because the battery cable was replaced with a standard cable. Owners don't always realize that what they think is just a mounting clamp, is in fact the ground. So they leave it out.
You should add back a body ground from your battery negative to the body metal. Either back to this same hole, or wherever it's more convenient. Usually people put it under one of the screws to the starter relay. But it's up to you.

Correct, it's been changed over the years and there is no ground from the battery to the body.

Your original description had you removing the regulator and doing some painting. Painting is a good thing, but wherever you have a grounding need, it's a bad thing. So whenever you paint near a component's mounting point, make sure that the screws and the body and the hole are clean and free of rust and paint. Things that have to be grounded have to stay grounded.

I didn't run the engine with the voltage regulator disconnected from the body. Would it still fry it not running? Battery was disconnected when I removed it to paint.

I still think that what happened was when you disconnected the regulator from the body, if the battery was still hooked up then you fried the regulator. Then when you started the engine the alternator "full fielded" causing it to put out it's maximum total amperage the whole time it was capable of it. That would explain the instance of smoking wires only when you revved the engine up to accelerate. At idle the alternator is only putting out maybe 20 amps or so, but at higher rpm and with a tight belt, it can output it's max at least. Probably in the 55-65a range.
Normally this is not near enough to cause a problem. But if the original Black w/yellow wire was compromised in any way (extra resistance through corroded firewall connectors, or the ammeter connector for two examples) the wire could not handle 60a for an extended period and overheated to the melting point.

That's my guess at this point anyway. Until other clues crop up.

Take a look at these pictures and tell me what you think, In the first picture, the charging wire has corrosion and the copper strands are a different color like they had been exposed for a while. In the second picture, the smaller ground wire that ran from the engine to underneath the relay bracket is in exactly the same place in the engine compartment when the wires overheated. The 3rd picture is the engine ground wire to the battery which was in the same are of the engine compartment as well where the short may have occurred. Thansk for your insight Paul!

Paul

 

[DirtDonk]

I'm referring to the ground wire that went to the engine and underneath the starter relay (the melted ground wire) as causing the short with the black/yellow wire, not the one from the alternator to the voltage regulator. Is that possible?

Ok, got it. I saw that in your other pics, but was having a hard time visualizing both ends of both grounds.
Yes, anything is possible. But you have to find out where they may have crossed and rubbed themselves bare enough to short.

Yes that's where I removed the relay, it was mounted there. I unscrewed it to get a better picture of the wiring. You can see where I cleaned the paint off.

Ah yes, the early models had their relays mounted there, while in the next year or two Ford moved them over to the side of the wheel well facing the battery.
It's possible that Ford used the same relay mounting bolt for the ground. That would have made sense. But while it probably did not come from the engine block like yours did, it's a perfectly legit place to mount it since it's touching the same ground cable. Just at a different point.
I'd sure like to see an original '69 right about now. Be nice to verify what was what and where.

Correct, it's been changed over the years and there is no ground from the battery to the body.

I didn't run the engine with the voltage regulator disconnected from the body. Would it still fry it not running? Battery was disconnected when I removed it to paint.

Then you would have been ok. It would still fry even with the key off because the Yellow wire is constant hot. But since the battery was disconnected, then there was no harm no foul.
Which brings us back to the shorted ground wire with the charge wire. Until something else crops up.

You still have to dig deeper and remove all the tape if you want to know what you need to do, but you're on a roll now so keep it up!

View attachment 872898 View attachment 872899 View attachment 872900
Take a look at these pictures and tell me what you think, In the first picture, the charging wire has corrosion and the copper strands are a different color like they had been exposed for a while. In the second picture, the smaller ground wire that ran from the engine to underneath the relay bracket is in exactly the same place in the engine compartment when the wires overheated. The 3rd picture is the engine ground wire to the battery which was in the same are of the engine compartment as well where the short may have occurred. Thansk for your insight Paul!

Can't tell for sure about it all, but your scenario sounds logical.
The color and look of the wire however can happen two ways. Long term exposure like you mention, OR just a quick burnout. The wire will literally take on a rusted and corroded and "overheat-blue" tone instantly upon this kind of overload.

If you ever happen to be "lucky" enough to see a wire overloaded and about to melt down, you'd be shocked at the contortions it goes through. It'll whip around, stiffen up either straight or crooked like it's having an epileptic seizure. If that goes on long enough it burns down.
Seen this many times when a main engine ground fails and someone turns the key to START. When the starter pulls it's massive load through smaller wires they stiffen up like snakes that have been instantly frozen in mid coil.

Very interesting to see, but you don't want it to be on one of your rigs!

Paul

 

[Blue1969]

Ok, got it. I saw that in your other pics, but was having a hard time visualizing both ends of both grounds.
Yes, anything is possible. But you have to find out where they may have crossed and rubbed themselves bare enough to short.

The alternator harness was in pretty bad shape, probably by previous wire routing and 50 years in the elements. I think you mentioned the ground wire was original, so there have been issues before. The rest of the wiring on the truck appeared to be in decent shape. I had actually taped a couple of spots on the alternator harness that were already bare before the new alternator install. I should've stopped then and replaced the alternator harness.

Ah yes, the early models had their relays mounted there, while in the next year or two Ford moved them over to the side of the wheel well facing the battery.
It's possible that Ford used the same relay mounting bolt for the ground. That would have made sense. But while it probably did not come from the engine block like yours did, it's a perfectly legit place to mount it since it's touching the same ground cable. Just at a different point.
I'd sure like to see an original '69 right about now. Be nice to verify what was what and where.

Me too! If anyone has an original 69 unrestored, I would love to see where the grounding wire from the engine is installed.

Then you would have been ok. It would still fry even with the key off because the Yellow wire is constant hot. But since the battery was disconnected, then there was no harm no foul.
Which brings us back to the shorted ground wire with the charge wire. Until something else crops up.

You still have to dig deeper and remove all the tape if you want to know what you need to do, but you're on a roll now so keep it up!

I'll start removing the taped harness up to the firewall and see how much collateral damage I have. I know without a doubt the charging wire will have to be replaced. Once I have the tape removed from the harness to the firewall, I'll ask for some guidance from there. I definitely have at least one wire melted under dash too, which I'm assuming is probably the same wire? My preference is to repair the damage done and drive it until I retire. I hope to retire sometime this upcoming year, when I'll start rebuilding the truck. If I end up having to replace the entire wiring harness now, the truck will have sit for a while. If I go to that kind of trouble, like taking the dash out, the truck's coming apart. By the way how much trouble is the dash removal? Do you remove the steering column too? My concern is rusted bolts or studs breaking off.

Can't tell for sure about it all, but your scenario sounds logical.

The color and look of the wire however can happen two ways. Long term exposure like you mention, OR just a quick burnout. The wire will literally take on a rusted and corroded and "overheat-blue" tone instantly upon this kind of overload.

The place I have circled in the charging harness, the wire looks oxidized just in that one area. The rest of the burnt wire has a completely different color, which leads me to believe it was exposed much earlier than when the short occurred. Also to support that, there is a small kink in the wire in that same area, which looks like the wire was pressed against something at some point. I believe the short occurred between that spot and the grounding wire to the engine. Based on how the wires were laid out in the engine compartment, this must be the cause. It seems as though everything points to that.

If you ever happen to be "lucky" enough to see a wire overloaded and about to melt down, you'd be shocked at the contortions it goes through. It'll whip around, stiffen up either straight or crooked like it's having an epileptic seizure. If that goes on long enough it burns down.
Seen this many times when a main engine ground fails and someone turns the key to START. When the starter pulls it's massive load through smaller wires they stiffen up like snakes that have been instantly frozen in mid coil.

Very interesting to see, but you don't want it to be on one of your rigs!

My hope is to never smell or see a burning wire again! I had no idea it reacted in such a manner, Thanks Paul!

Paul

 

[DirtDonk]

If you are right about the long-term exposure, then that corrosion also added resistance to electricity moving through the wire. Literally if you turn it into verbal equation, resistance equals heat and heat equals resistance. The more of one you add to the equation the more of the other one increases.
If you put enough power into a wire and it’s got enough resistance it will literally burn itself out.

Perhaps the added resistance in the wire along with your new alternator that was perhaps capable of putting out more power than the old one, it was just a bad combination waiting to happen.
This would also at least be consistent with your first experience that the smoke was occurring as you revved the engine up more. The alternator can’t put out that much current at lower RPM, but at higher RPM it can put out its maximum output if called on to do so.

 

[Blue1969]

If you are right about the long-term exposure, then that corrosion also added resistance to electricity moving through the wire. Literally if you turn it into verbal equation, resistance equals heat and heat equals resistance. The more of one you add to the equation the more of the other one increases.
If you put enough power into a wire and it’s got enough resistance it will literally burn itself out.

Perhaps the added resistance in the wire along with your new alternator that was perhaps capable of putting out more power than the old one, it was just a bad combination waiting to happen.
This would also at least be consistent with your first experience that the smoke was occurring as you revved the engine up more. The alternator can’t put out that much current at lower RPM, but at higher RPM it can put out its maximum output if called on to do so.

Thanks Paul, I'll get the harness un-taped and have a look. I appreciate all of your insight.

 

[Steve83]

Corrosion along the surface of a wire adds virtually zero resistance, until the cross-sectional area of the wire's metal is significantly reduced. Corrosion between the wire & its terminal, or between 2 terminals adds a LOT of resistance. Heating a wire adds zero resistance, until the metal begins to liquefy (~1,500°F for Copper). Heat is produced by current (Amps) passing through resistance. The highest temperature occurs where resistance is highest. If the whole wire gets hot, then the wire has generally-equal resistance along that entire length (no significant corrosion or other damage).

 

[Blue1969]

How do the 2 rectangular plugs at the firewall In the engine wiring harness disconnect?