My alternator wire melted.

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N1ce2k1llu

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I have a 1971 plymouth scamp. I was tuning my carb after a cam swap when I noticed flashing coming from inside my alternator then my engine died and white smoke was pouring out from the harness. Even with the engine dead it kept burning until I disconnected the battery. The blue wire that plugs to the alternator field melted all the way to the firewall plug. It splits off to the voltage regulator but that wire didn't melt. The green wire that comes out of the regulator that goes back to the second field had broken strands at the connecter and broke off after a couple of wiggles. I also found corrosion inside the firewall plug. So I'm thinking it must be one of the two that caused it but not 100%. Anybody have input. BTW it's a new alternator with 2 engine hours on it.
 
The blue wires are branched off the "ignition run" which IS NOT FUSED. That IGN1/ run feeds several items depending on year / model

Feeds power to ignition system
to VR
to alternator field
to electric choke if used
emissions doo dads on some years

MOST LIKELY you have a short in that blue wire or right IN the alternator. The two field connections at the alternator should show continuity between the two of them, but NOT to ground (case) of the alternator

You will be lucky if you didn't burn up "some other" wire. I would get under the dash and try to trace the "ign1" where it comes out of the bulkhead and goes to the ignition switch.
 
Not long ago I found a melted connector under the dash. It was the connecter for my steering column, thick red wire heated up so much it melted it's way out of the plastic connector. Looks like I'm rewiring every thing now. Thanks for reply.
 
Also check and clean all of the electrical connectors at the firewall and the connections to all of the accessories on your car. It will take some time but you will be surprised at what you will find after 40 + years., Use plenty of Dielectric grease on all of the connections after you have cleaned them. Poor grounds and loose electrical connections were a major problem in the 60's and 70"s.
Charging System Upgrade with a Tuff Stuff Alternator - Hot Rod Network
 
I would do what Del said and trace the wires under the dash and look for the insulation melted off... I would start with the amp gauge wires and go from there...
 
Unfortunately new does not always mean good. Sorry to read about this.
Since turning the ignition off did not kill the power to the fire, at least one failure was the battery feed shorting to ground inside the alternator. Fusible link should have gone first, so maybe other things going on as well. (see example Fusible Links in Charging Systems with Ammeter)

On your alternator - regulator setup, the green wire goes to ground through the regulator. That's how those regulators control the voltage.
67dart273 I think covered the rest.
 
Unfortunately new does not always mean good. Sorry to read about this.
Since turning the ignition off did not kill the power to the fire, at least one failure was the battery feed shorting to ground inside the alternator. Fusible link should have gone first, so maybe other things going on as well. (see example Fusible Links in Charging Systems with Ammeter)

On your alternator - regulator setup, the green wire goes to ground through the regulator. That's how those regulators control the voltage.
67dart273 I think covered the rest.
The ignition was still keyed on, the motor just died and the first instinct was to disconnect the battery. I changed my instrument cluster to digital and ran my own wire straight to the battery for my volt meter. That's what an ammeter is, right? Or did I wire my stuff wrong :/
 
The ignition was still keyed on, the motor just died and the first instinct was to disconnect the battery. I changed my instrument cluster to digital and ran my own wire straight to the battery for my volt meter. That's what an ammeter is, right? Or did I wire my stuff wrong :/
oh.
Factory instrumentation:
* Uses a 5 volt regulator for the fuel level, coolant temperature and oil pressure lamp or gage .
* There is no voltmeter. A voltmeter will show Potential energy level between two points, one usually being ground. Power can not be sent through a voltmeter. Wiring a voltmeter in-line will destroy it.
* Ammeter measures current flow through a wire. Most ammeters have an internal shunt that actually carries the current. (Some later cars did have external shunts, but the point here is with a typical ammeter wired in-line. Power goes in one terminal and out the other.)

Its probably worth going over this:
Volts are potential energy. Like water in a big holding tank on a roof, even when the electricty is not flowing, it has potential to flow. In fact if we punched a big hole in the side, so much would come out it would knock a person down who tried to stop it from reaching the ground. Same idea with a battery. But what knocks him down? The water being 14 feet above ground? No. Its the hundreds of gallons rushing out of that hole 14' above ground.
Amps are a measurement of flow. If a tap at the bottom of that water tank is opened, the flow into a hose can be described in gallons per minute.

The ammeter shows how much flow is making its way from the battery to the main junction, or how much current is flowing to the battery to charge it.

In the typical automotive setup with an ammeter, the battery is connected to the rest of the system through the charging wire. Everything downstream of the battery was protected by a fusible link in that wire. If you are going to use a different wiring strategy, it still will need protection on each and every wire downstream from the battery. If you compare the 1985 wiring with the 1986 SJ Jeeps wiring you can see how that was done in a single wire (ammeter) vs an engine side distribution (voltmeter). diagrams here:
1985 AMC Jeep SJ Charging and Headlight Wiring Diagrams
 
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The ignition was still keyed on, the motor just died and the first instinct was to disconnect the battery. I changed my instrument cluster to digital and ran my own wire straight to the battery for my volt meter. That's what an ammeter is, right? Or did I wire my stuff wrong :/

No, ammeters and volt meters are wire different...

Ammeters go in series, volt meters go in parallel with the current...
 
Unfortunately new does not always mean good. Sorry to read about this.
Since turning the ignition off did not kill the power to the fire, at least one failure was the battery feed shorting to ground inside the alternator. Fusible link should have gone first, so maybe other things going on as well. (see example Fusible Links in Charging Systems with Ammeter)

On your alternator - regulator setup, the green wire goes to ground through the regulator. That's how those regulators control the voltage.
67dart273 I think covered the rest.
I have a 1971 plymouth scamp. I was tuning my carb after a cam swap when I noticed flashing coming from inside my alternator then my engine died and white smoke was pouring out from the harness. Even with the engine dead it kept burning until I disconnected the battery. The blue wire that plugs to the alternator field melted all the way to the firewall plug. It splits off to the voltage regulator but that wire didn't melt. The green wire that comes out of the regulator that goes back to the second field had broken strands at the connecter and broke off after a couple of wiggles. I also found corrosion inside the firewall plug. So I'm thinking it must be one of the two that caused it but not 100%. Anybody have input. BTW it's a new alternator with 2 engine hours on it.
The blue wires are branched off the "ignition run" which IS NOT FUSED. That IGN1/ run feeds several items depending on year / model

Feeds power to ignition system
to VR
to alternator field
to electric choke if used
emissions doo dads on some years

MOST LIKELY you have a short in that blue wire or right IN the alternator. The two field connections at the alternator should show continuity between the two of them, but NOT to ground (case) of the alternator

You will be lucky if you didn't burn up "some other" wire. I would get under the dash and try to trace the "ign1" where it comes out of the bulkhead and goes to the ignition switch.
Wouldn't you know I read straight to ground on fields 1&2. Now my question is that why the wire melted? Would a short somewhere else cause the short on the fields? To recap, engine running, notice flashing inside alternator, engine dies, wire starts to melt, (with ignition still keyed on) stops melting when I disconnect battery. One more thing, voltage regulator mounted on firewall reading from regulator case to ground was not constant.
 
Really hard to know how you wired it up.
Take one of those diagrams that I or Nacho drew and use them as a basis to draw what you did to your '71. Modify in MS Paint or print it and use colored pencils or whatever. Then look for the evidence of were it overheated and you can figure out what happened. And if its still not clear, you can post the drawing and photos.
 
I haven't checked visually under the dash yet only felt for hot wires when this happened.

20180411_215755-1.jpg
 
Wouldn't you know I read straight to ground on fields 1&2. Now my question is that why the wire melted? Would a short somewhere else cause the short on the fields? To recap, engine running, notice flashing inside alternator, engine dies, wire starts to melt, (with ignition still keyed on) stops melting when I disconnect battery. One more thing, voltage regulator mounted on firewall reading from regulator case to ground was not constant.

No the field is shorted to ground, and THAT is what caused the damage. Pull the alternator and pull the brushes and inspect
 
No the field is shorted to ground, and THAT is what caused the damage. Pull the alternator and pull the brushes and inspect
It's crazy because it's a new alternator only used about an hour. Thanks for your time and help.
 
So you think maybe a fault in the alternator is/was the only fault? Maybe your aftermarket ignition addition was drawing too much current on the blue wire?
This same connector meltdown does happen in bone stock examples. Mostly in those that have electric choke assist added to the barely adequate wire and connectors. No alternator fault found.
In my opinion, every owner should cut the blue wire just beyond the bulkhead connector and add a relay there, along with fuses in the branch circuits. Afterwards, a fault in the electric choke, alternator, ignition system, will blow the added fuses or melt wires only to the relay and not into the cabin.
There have been cases where the wire that feeds the fuse box is melted down. Combined amp load of a/c, blower, wipers, etc..., can overheat this wire but it is less common due to those being fused branch circuits.
The blue wire feeds a bunch of stuff without a fuse in any branch ( other than the spot on a inst' panel circuit that serves as a fusible link ).
Bottom line... No matter how you go about repairing the ignition switch harness connector meltdown... add a relay to blue.
Get full 12 volts to charging system components and ignition system components.
And by the way... I don't know what year model started the engine harness connector near blower motor so you should look for and inspect it. These meltdown also. This connector was added only for universal ease of assembly ( The different engines would plug and play ).
We can clip, crimp, solder, and heat shrink to delete this connector.
I want to add fuses but don't know amps on the components. I have 3 bulkhead connectors on the drivers side. I did notice awg size difference between old and new ignition connector.
 
So you think maybe a fault in the alternator is/was the only fault? Maybe your aftermarket ignition addition was drawing too much current on the blue wire?
This same connector meltdown does happen in bone stock examples. Mostly in those that have electric choke assist added to the barely adequate wire and connectors. No alternator fault found.
In my opinion, every owner should cut the blue wire just beyond the bulkhead connector and add a relay there, along with fuses in the branch circuits. Afterwards, a fault in the electric choke, alternator, ignition system, will blow the added fuses or melt wires only to the relay and not into the cabin.
There have been cases where the wire that feeds the fuse box is melted down. Combined amp load of a/c, blower, wipers, etc..., can overheat this wire but it is less common due to those being fused branch circuits.
The blue wire feeds a bunch of stuff without a fuse in any branch ( other than the spot on a inst' panel circuit that serves as a fusible link ).
Bottom line... No matter how you go about repairing the ignition switch harness connector meltdown... add a relay to blue.
Get full 12 volts to charging system components and ignition system components.
And by the way... I don't know what year model started the engine harness connector near blower motor so you should look for and inspect it. These meltdown also. This connector was added only for universal ease of assembly ( The different engines would plug and play ).
We can clip, crimp, solder, and heat shrink to delete this connector.
I am very interested in your relay / fuse idea. If you could draw it out or something to were I have a clear understanding, that would be great.
 
The blue wires are branched off the "ignition run" which IS NOT FUSED. That IGN1/ run feeds several items depending on year / model

Feeds power to ignition system
to VR
to alternator field
to electric choke if used
emissions doo dads on some years

MOST LIKELY you have a short in that blue wire or right IN the alternator. The two field connections at the alternator should show continuity between the two of them, but NOT to ground (case) of the alternator

You will be lucky if you didn't burn up "some other" wire. I would get under the dash and try to trace the "ign1" where it comes out of the bulkhead and goes to the ignition switch.

I know these posts are 3yrs old.
"The two field connections at the alternator should show continuity between the two of them, but NOT to ground (case) of the alternator"

I think this just answered my question though. Brand new alt and the blue fild wire melted when I turned on the key and I have continuity between fild post and ground which if I'm reading correct it means the alt is bad then correct?
Would this have also fried my VR?
 
If its an isolated field alternator then there should be no continuity between either field terminal and ground.
If its a grounded field alternator then there should be continuity between the insulated terminal and the ground.
See if this info in this link helps Identifying Chrysler Alternators (1960-1976)
Both the how it should be, and how rebuilders screw with them.
 
If its an isolated field alternator then there should be no continuity between either field terminal and ground.
If its a grounded field alternator then there should be continuity between the insulated terminal and the ground.
See if this info in this link helps Identifying Chrysler Alternators (1960-1976)
Both the how it should be, and how rebuilders screw with them.

It's the square back which from every thing I have read the field should not be grounded luckily it just fried the blue wire to the point it splices into the other wires and didn't melt the bulkhead fitting
 
I know these posts are 3yrs old.
"The two field connections at the alternator should show continuity between the two of them, but NOT to ground (case) of the alternator"

I think this just answered my question though. Brand new alt and the blue fild wire melted when I turned on the key and I have continuity between fild post and ground which if I'm reading correct it means the alt is bad then correct?
Would this have also fried my VR?
This problem seems to be entirely too prevalent. A rebuilt alternator with incorrect or incorrectly installed brush mounting hardware. You have a 50-50 chance. If you get the green hooked to the shorted (to ground) brush, it will merely overcharge badly until you realize. If you connect the blue to the short, it will burn something down.

CORRECT isolated field alternator will show low resistance between the two field wires and OPEN (infinity) from either one to the case

Many times you can SEE the problem if you carefully examine the brushes by eye
 
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