Voltage regulator to field wire up in smoke

So I kind of need some help... I have a 72 charger 318 that was a no crank/no start. Put a new battery and she Car cranks like new... A couple pumps from the accelerator and runs like a champ for about 5 seconds when I notice smoke and cut the engine off. The dark blue wire from the voltage regulator to the alternator is fried and a blue wire from the resistor ballast looks like she was smoking too but not melted. Any ideas on where to go from here? I Don't have access to the car all the time "reasons" and don't want to throw parts at it that's not needed. What test should I do to find out why this happened? And is the wire from the ballast and the regulator connected?

One of the feilds in my alt was bad. Happened in my 1971 Challenger. I had to put new alt figured a new regulator. Since needed a new engine bay harness.
Was no fun since just we had left my wedding reception

Lets start at the beginning...

72
Dodge
Charger
318


What modifications have been done to the car (especially in the engine compartment, under the dash and to the electrical)

Where did the smoke come from ( under dash in the engine compartment?)

do you have a wiring diagram?
mymopar.com
classiccarwiring.com

Watch this video



You should have an electronic voltage regulator. The way they work is one wire with full battery voltage (Blue?) goes to one of the field terminals on the alternator. Another wire (green?) from the other field terminal goes to the voltage regulator where it goes through circuity to produce a variable ground to very the field strength to modulate the output of the alternator.

If the alternator was changed recently the wrong year alternator may have been put in. older cars (69 and older????) used a ground field alternator. Rebuilders are short on round back alternator cores and use a square back core but they ground one of the terminals to convert it to be a functional equivalent to a round back.

to test the alternator remove both field wires and check for low numerical ohms on each field terminal to ground. any reading other than "OL" or what ever your gauge reads when both leads are not touching each other indicates the alternator might be bad.


you said the blue wire is fried, from where to where? can you see its entire length?

if it is in a wiring harness and it melted / fried it is very likely that other wires in contact with it are also fried.

What ever happened suggests you have a direct short somewhere. if you have an electronic choke look at that wire as it might have fallen off and is shorting to the Manifold

you will have to trace out the problem there is no magic bullet we can share. every failure with these old cars is unique to your car.

good luck

I agree with everything Dana wrote in the previous post. Since you wrote ballast resistor singular, I'll assume this is a points igniton for the moment.

6one9er said:

The dark blue wire from the voltage regulator to the alternator is fried and a blue wire from the resistor ballast looks like she was smoking too but not melted.

Click to expand...

Blue wire is the "ignition run" and labelled J2 on the wiring diagrams.
Ignition run is switched on by the key and supplies power to the coil, and the alternator field. A branch goes to the voltage regulator so it can sense what voltage the system is at.

Melting wire indicates a short. Most likely shorted to ground. Follow the melted blue wire right up the the end of where ever it goes. That's going to be close to the short. If the wire has chafed against some metal - that will be the cause. It's melted at the terminal, remove the terminal and brush. Maybe it lost its insulator.

The ignition run circuit look something like this. Whether you car has a welded splice as shown, or the wires are joined at a terminal, you'll have to tell us.

Sounds like the blue wire is attached to a ground terminal at the alternator.

Is there a plastic insulator on both alternator terminal connections?

hotrod swinger said:

Sounds like the blue wire is attached to a ground terminal at the alternator.

Is there a plastic insulator on both alternator terminal connections?

Click to expand...

Could be. But there shouldn't be a grounded field terminal on a '72.

After the op reports back we all will have something to go by.

As far as modifications on the car... There are none. The car only has 37,000 og miles on it. I turned the car on... Drove for 30 min + on the highway and when I backed it up in the storage "no mice there it's a clean storage area" turned it off then I noticed I wanted to back it up a little more. Went to turn it on and No crank, no lights... Nothing. Couple days ago went back to take a look, dead battery (weird but didn't think too much about it) put a new one in and up in smoke she went.
Thanks for all the help I really appreciate it I will get a chance to take another look at her this weekend and will want to test a couple of components before trying to slap any parts on her... First is to replace that dark blue wire from the alternator field to the voltage regulator and ballast resistor exc, that took the most damage. I will do some test after that...
Thanks for all the help guys I really do appreciate it
FYI the picture is only for reference not my actual car, only showing the route I believe the wire that smoked up was connected to... At least as far as I can tell from memory

Dana67Dart said:

Lets start at the beginning...

72
Dodge
Charger
318


What modifications have been done to the car (especially in the engine compartment, under the dash and to the electrical)

Where did the smoke come from ( under dash in the engine compartment?)

do you have a wiring diagram?
mymopar.com
classiccarwiring.com

Watch this video



You should have an electronic voltage regulator. The way they work is one wire with full battery voltage (Blue?) goes to one of the field terminals on the alternator. Another wire (green?) from the other field terminal goes to the voltage regulator where it goes through circuity to produce a variable ground to very the field strength to modulate the output of the alternator.

If the alternator was changed recently the wrong year alternator may have been put in. older cars (69 and older????) used a ground field alternator. Rebuilders are short on round back alternator cores and use a square back core but they ground one of the terminals to convert it to be a functional equivalent to a round back.

to test the alternator remove both field wires and check for low numerical ohms on each field terminal to ground. any reading other than "OL" or what ever your gauge reads when both leads are not touching each other indicates the alternator might be bad.


you said the blue wire is fried, from where to where? can you see its entire length?

if it is in a wiring harness and it melted / fried it is very likely that other wires in contact with it are also fried.

What ever happened suggests you have a direct short somewhere. if you have an electronic choke look at that wire as it might have fallen off and is shorting to the Manifold

you will have to trace out the problem there is no magic bullet we can share. every failure with these old cars is unique to your car.

good luck

Click to expand...

Thanks and you are right that it is the blue wire and and the alternator is a square back but my old man said he never did any modifications or had to change any components before he passed and left me the car 6 yrs ago. I've never had to do any part swaps since I've had her other than regular maintenance and a drive around the block so she doesn't sit for too long.The blue wire is in a harness basically the entire length of the engine but it was melted at the alternator and I could see smoke coming from the blue wire at the ballast resistor and at the voltage regulator which also got hot as it looked like she was smoking (not 100% sure on that because it could've been the wire attached to it). Only smoke was coming from engine compartment. I will replace the blue wire and will get a good look at the rest of the harness while I'm there.. I thank you for the wisdom and will proceed to bench test the alternator. As far as electric choke.. not too sure about that as I don't know much about these older cars like that. How can I (bench)test the regulator? Oh picture for reference of the blue wire route (not my car fyi)

6one9er said:

. How can I (bench)test the regulator

Click to expand...

No way I know of without special Chrysler tools


Before you remove anything I would look for the short.

The do tests before t you reconnect anything

6one9er said:

First is to replace that dark blue wire from the alternator field to the voltage regulator and ballast resistor exc, that took the most damage.

Click to expand...

Dana67Dart said:

Before you remove anything I would look for the short.

Click to expand...

I would examine all of the connecting points for the J2 wire and both power feeds (R6, A1). The shop manual will show where those wires connect.*

I'd also remove the alternator for closer examination. Fortunately all of the parts are pretty easy to access and replace on a squareback. If the rotor is not damaged the replacing parts is easy and it will be better than what is sold over the counter. If you have a multimeter, check each field terminal to be sure they are not connecting to ground. We can go into depth later. its in the shop manual too.

6one9er said:

dead battery (weird but didn't think too much about it) put a new one in and up in smoke she went.

Click to expand...

6one9er said:

but it was melted at the alternator and I could see smoke coming from the blue wire at the ballast resistor and at the voltage regulator which also got hot as it looked like she was smoking (not 100% sure on that because it could've been the wire attached to it).

Click to expand...

Did it go up in smoke when the new battery was installed or when the engine was running?

These are the questions that have to be answered to track down the fault.
I'm going to assume you did not look at the ammeter, labelled"alternator". If it had been pointing to charge, I'd suspect high or uncontrolled voltage, and if it was showing discharge, then a short and/or alternator failure.

Since you're new to this, lets start here.
Take your finger or mouse pointer and follow the wire from the battery positive to the key switch.

Everything connected to that line is electrically hot. When the key is run, as shown in the diagram, then ignition wire is hot.
If it the short was in that circuit, it should have only occurred when the key was turned to run.
When the engine is running, power comes from the alternator down the R6 wire. Take your pointer and follow that to the main splice (black circle). Then it goes to the key switch along the J1 wire. If the battery needs recharging, some current will also flow to it and the ammeter will show charging.

Now lets go to the "ignition run" wire. The J2 wire connection at the voltage regulator is for sensing only. The power to create the alternator's electromagnetic field goes through the J2 wire to the alternator, and then out through the R3 wire. The regulator connects the R3 wire to ground. The VR switches the connection on and off as needed to maintain 14.2 Volts.

---------------------------------------------
* How to use the wiring diagram from the shop manual.

Example. We want to know about the condition of J2 at the bulkhead connection.
Here's the connector.



On the engine wiring diagram, follow wire J2 back to the connector.

The leads to position 23 on the connector.


Electric choke. Just look for electric wires going to either side of the carburetor. if so, we'll come to this.

Mattax said:

I would examine all of the connecting points for the J2 wire and both power feeds (R6, A1). The shop manual will show where those wires connect.*

I'd also remove the alternator for closer examination. Fortunately all of the parts are pretty easy to access and replace on a squareback. If the rotor is not damaged the replacing parts is easy and it will be better than what is sold over the counter. If you have a multimeter, check each field terminal to be sure they are not connecting to ground. We can go into depth later. its in the shop manual too.



Did it go up in smoke when the new battery was installed or when the engine was running?

These are the questions that have to be answered to track down the fault.
I'm going to assume you did not look at the ammeter, labelled"alternator". If it had been pointing to charge, I'd suspect high or uncontrolled voltage, and if it was showing discharge, then a short and/or alternator failure.

Since you're new to this, lets start here.
Take your finger or mouse pointer and follow the wire from the battery positive to the key switch.
View attachment 1716221278
Everything connected to that line is electrically hot. When the key is run, as shown in the diagram, then ignition wire is hot.
If it the short was in that circuit, it should have only occurred when the key was turned to run.
When the engine is running, power comes from the alternator down the R6 wire. Take your pointer and follow that to the main splice (black circle). Then it goes to the key switch along the J1 wire. If the battery needs recharging, some current will also flow to it and the ammeter will show charging.

Now lets go to the "ignition run" wire. The J2 wire connection at the voltage regulator is for sensing only. The power to create the alternator's electromagnetic field goes through the J2 wire to the alternator, and then out through the R3 wire. The regulator connects the R3 wire to ground. The VR switches the connection on and off as needed to maintain 14.2 Volts.

---------------------------------------------
* How to use the wiring diagram from the shop manual.

Example. We want to know about the condition of J2 at the bulkhead connection.
Here's the connector.


View attachment 1716221286
On the engine wiring diagram, follow wire J2 back to the connector.
View attachment 1716221288
The leads to position 23 on the connector.


Electric choke. Just look for electric wires going to either side of the carburetor. if so, we'll come to

Click to expand...

Mattax said:

I would examine all of the connecting points for the J2 wire and both power feeds (R6, A1). The shop manual will show where those wires connect.*

I'd also remove the alternator for closer examination. Fortunately all of the parts are pretty easy to access and replace on a squareback. If the rotor is not damaged the replacing parts is easy and it will be better than what is sold over the counter. If you have a multimeter, check each field terminal to be sure they are not connecting to ground. We can go into depth later. its in the shop manual too.



Did it go up in smoke when the new battery was installed or when the engine was running?

These are the questions that have to be answered to track down the fault.
I'm going to assume you did not look at the ammeter, labelled"alternator". If it had been pointing to charge, I'd suspect high or uncontrolled voltage, and if it was showing discharge, then a short and/or alternator failure.

Since you're new to this, lets start here.
Take your finger or mouse pointer and follow the wire from the battery positive to the key switch.
View attachment 1716221278
Everything connected to that line is electrically hot. When the key is run, as shown in the diagram, then ignition wire is hot.
If it the short was in that circuit, it should have only occurred when the key was turned to run.
When the engine is running, power comes from the alternator down the R6 wire. Take your pointer and follow that to the main splice (black circle). Then it goes to the key switch along the J1 wire. If the battery needs recharging, some current will also flow to it and the ammeter will show charging.

Now lets go to the "ignition run" wire. The J2 wire connection at the voltage regulator is for sensing only. The power to create the alternator's electromagnetic field goes through the J2 wire to the alternator, and then out through the R3 wire. The regulator connects the R3 wire to ground. The VR switches the connection on and off as needed to maintain 14.2 Volts.

---------------------------------------------
* How to use the wiring diagram from the shop manual.

Example. We want to know about the condition of J2 at the bulkhead connection.
Here's the connector.


View attachment 1716221286
On the engine wiring diagram, follow wire J2 back to the connector.
View attachment 1716221288
The leads to position 23 on the connector.


Electric choke. Just look for electric wires going to either side of the carburetor. if so, we'll come to this.

Click to expand...

Yeah the wire melted when she was running not when I connected the battery. I had the battery connected for about 13 min before trying to start her up. But No I didn't look at the ammeter I ran out of time and had to head out. thanks for taking the time to explain all that I will check the car out this weekend and let everyone know what happened...