Electrical issue

[steve from staten island]

On the firewall harness connection block. The middle connections. There is a blue wire with ring terminal that goes to starter relay. It says "fusible link". The insulation on it melted. I believe it was still connected as I checked continuity and it was ok. The male spade connector is all disclosed from heat......Also in that block is a black wire that runs to the alternator, that connection looked like it got hot also.
The amp meter works but is showing a discharge condition. A voltmeter check at the battery confirmed the battery is not charging.
The wiring is brand new, the amp meter was restored, the circuit breaker for amp meter is new. Everything is new. Any ideas will be appreciated greatly.

 

[MoparLeo]

Is your question about why the battery terminal does not show a charge when running ? Go back to the alternator and check out put there first. If none, replace. If yes, follow the wires to the battery. Check for continuity at both ends of the fusible link wire. It is just that, a fuse built into the wire. It could be shorted.

 

[steve from staten island]

My thoughts are that the alternator black wire runs to the amp meter as does the fusible link. Im leaning towards the amp meter . '
A no charge issue should have not melted that wire. The other issue is now I have to eliminate that connection as the male and female spade are no good. I probably am going to have to wire right to the amp meter and eliminate that connection at the junction box.
My question is still why did that wire insulation melt

 

[moobster]

Yes, the black wire from the alternator goes through the firewall to one side of the amp meter. The red wire from the starter relay goes through the firewall and feeds the other side of the amp gauge, it also feeds the ignition switch and the fuse panel.

 

[steve from staten island]

Yes, the black wire from the alternator goes through the firewall to one side of the amp meter. The red wire from the starter relay goes through the firewall and feeds the other side of the amp gauge, it also feeds the ignition switch and the fuse panel.

Just was out there looking things over. So if I tied the alternator wire right to the starter rely, bypassing the amp meter. Im thinking it may be a bad connection at fire wall.

 

[Demonic]

Im thinking it may be a bad connection at fire wall.

It's a well know problem spot. Mine let go after 48 years, two years ago. Read here, around post 6:

https://www.forabodiesonly.com/mopar/threads/charging-issues.173673/

 

[texas69bee]

What size alternator are you using, did you upgrade the size from an original? If so then you need to upgrade the size of the wire. I would of ditched the idea of using the amp meter and converted everything to a volt meter. You have a full load passing through the bulk head.
http://madelectrical.com/electricaltech/amp-gauges.shtml

 

[steve from staten island]

The car is just restored, today I took it out for maybe a mile or two with the AC on. When pulling back into the driveway I noticed according to Amp meter it was not charging. The blue fusible link wire is toast as is the connection at bulkhead. In that same connection block the black wire which is output from alternator to amp meter showed signs of overheating.
Of course I will look at all under hood wiring just to be sure nothing shorted out.
The problem with no charge is concerning as even though the fusible link wire insulation was burnt the car was still running and the amp meter worked.
So im now thinking pull the alternator and get it bench tested. Its a rock auto unit and I do hear a little whine in it.
The fusible link wire to bulkhead connection is no good. I will have to drill out the terminal and run a new wire from the fusible link to back of amp meter.
I intend on doing the same thing with the black alternator wire at the bulkhead. I want to eliminate that spade to spade connection.
I will send out the instrument cluster (again) and do a amp to volt meter conversion
The question id like to know is what good is that fusible link when it didn't really work and the connection at the bulkhead got so hot it destroyed the connections.
Should I install a circuit breaker in the line before it connects to the starter relay.
As I said everything was or is new and tight, if it was 40 years old I could accept this but its not.
This car has fought me tooth and nail every step of the way, its like it wants to beat me. Thanks for the help

 

[miller]

The question id like to know is what good is that fusible link when it didn't really work and the connection at the bulkhead got so hot it destroyed the connections.

In a way, the fusible link did work, though not completely. All it is, is a short piece of wire, smaller than the wire gauge it's connected to.
Yes, have the alternator tested. I'd also check the voltage regulator, too. All the wiring in that circuit, and mainly the connections at the ammeter. That's usually the start of problems...bad connections. Unless the wire sizes are too small for the loads. Positively at the firewall block, that gets the most damage.

Doing my 64, with a bigger 80 amp alternator, still using the stock ammeter, I added a parallel circuit w/2 fusible links. One each for the black/red feeds. But, that's another story.

What happened on yours is typical, if everything in that circuit isn't perfect. Good luck on it!

 

[moparnation74]

The fusible link did do its job.......

The no charging situation could ultimately be the alternator being the culprit.....As Jason noted above if you upgraded the alternator to a higher AMP it will be beneficial to upgrade the wire....

Once I went to Volts I never looked back at an AMP gauge......If the AMP gauge is bad you can bypass it temporarily by attached the red and black wires together with a small bolts and wrap it with electrical tape......If it was the gauge then something made contact and shorted it...

 

[texas69bee]

Just cause the wire is new does not mean it can carry the load. Match the GAUGE of the wire with the output of the alternator. As others have stated the fusible link did its job but it may also be rated to low if you went to large with the alternator.
I haven’t see you post your output yet.
Did you replace it with a round back alternator or a square back?
Do you have it set up as a one wire or two wire?
Is it properly grounded to the car?
If one wire, is the other terminal properly grounded to the case?
Far as not charging, bench testing is a good place to start and then the voltage regulator.
Good luck!

 

[steve from staten island]

Just cause the wire is new does not mean it can carry the load. Match the GAUGE of the wire with the output of the alternator. As others have stated the fusible link did its job but it may also be rated to low if you went to large with the alternator.
I haven’t see you post your output yet.
Did you replace it with a round back alternator or a square back?
Do you have it set up as a one wire or two wire?
Is it properly grounded to the car?
If one wire, is the other terminal properly grounded to the case?
Far as not charging, bench testing is a good place to start and then the voltage regulator.
Good luck!

I don't know the output of alternator, it was a Rock Auto replacement. Two wire with a electronic voltage regulator. All grounds are new and tight.
Im going to get alternator tested asap.
The other thing is the alternator output wire (black) were it goes into the firewall box also showed signs of overheating. Im hoping somehow the alternator output fried the link. There is no dead shorts as far as I can tell. No sparking when the positive battery terminal touches the battery terminal. Thanks for your help, I really appreciate it

 

[steve from staten island]

Ok,, on the positive side of the coil, wire going to it has slight ground...In other words a continuity tester lights up but a little dim.
I traced it back to the electronic voltage regulator and the side opposite the field connection, when I remove the connection ground at battery goes away. When I touch that terminal with continuity tester to ground the tester lights, not fully bright but it lights....Is Voltage regulator bad?

Wiring at amp meter under dash looks good...Im thinking a over charge situation caused a over heating at fusible link....

 

[threewood]

My thoughts are that the alternator black wire runs to the amp meter as does the fusible link. Im leaning towards the amp meter . '
A no charge issue should have not melted that wire. The other issue is now I have to eliminate that connection as the male and female spade are no good. I probably am going to have to wire right to the amp meter and eliminate that connection at the junction box.
My question is still why did that wire insulation melt

They seem to melt from high resistance in the connections. Loose or corroded = high resistance = heat. Remove the Packard connections in the wire bulkhead harness for the amp feed and make it a solid wire straight through (leave some extra in case it needs to come apart again). Replace the fusible link as well. The red wire from Bat + runs through the bulkhead to the ammeter and the Black + wire from ammeter runs to the alternator back through the bulkhead with the fuse box and other accessories attached to the black side. Bad connection will melt those big wires easily.

Check out the MAD bypass. Only downside is you bypass the ammeter but it can still wire to a volt meter.

 

[steve from staten island]

They seem to melt from high resistance in the connections. Loose or corroded = high resistance = heat. Remove the Packard connections in the wire bulkhead harness for the amp feed and make it a solid wire straight through (leave some extra in case it needs to come apart again). Replace the fusible link as well. The red wire from Bat + runs through the bulkhead to the ammeter and the Black + wire from ammeter runs to the alternator back through the bulkhead with the fuse box and other accessories attached to the black side. Bad connection will melt those big wires easily.
View attachment 794528

Check out the MAD bypass. Only downside is you bypass the ammeter but it can still wire to a volt meter.
View attachment 794529

What I dont understand in the bottom diagram is the connection for the black and red wires. It looks as if there both tied together. Why would the red wire even be needed?

 

[threewood]

What I dont understand in the bottom diagram is the connection for the black and red wires. It looks as if there both tied together. Why would the red wire even be needed?

It's not, really. But it is already there and effectively doubles the size of the wire carrying the load to the interior. I did the mod and have had zero issues. Only drawback is the loss of use of the ammeter. I modified a voltmeter to fit on the original ammeter mount in the dash so it looks stock.

But I think you would be light years ahead if you removed the connections for the red and black wires at the bulkhead and took the wires straight through.

 

[Crackedback]

Not a fan of the mad approach.

When I sell a wire around cable, I suggest leaving all the OEM wiring in place if the bulkhead is in good condition and bypass the ammeter. Run a voltmeter and move on.

 

[Wietse]

The matter of how many amps the alternator is does not matter at all, if it is a 50 or 500 amp alternator.
It only gives what is asked for by the electrical system.
So melting/burnt cables and connections is not the cause by what was giving the power but what has been demanding that power?
Did you run a lot of electrical consumers?
Charging battery, running A/C and adding a set of high output head lights could be enough to burn something.
Too much draw of electrical power heats up poor connections and thin wires, exactly what happened to you.
The fire wall connector is known to be a weak point, same for the amp gauge...possible root causes of burnt connections/fire in worse case scenario.
All electrical wiring is new, does not mean it is good but lets assume these things are tested before leaving the factory.
Did you add any big power consumers? (stereo, high power head lights, etc)

 

[steve from staten island]

The matter of how many amps the alternator is does not matter at all, if it is a 50 or 500 amp alternator.
It only gives what is asked for by the electrical system.
So melting/burnt cables and connections is not the cause by what was giving the power but what has been demanding that power?
Did you run a lot of electrical consumers?
Charging battery, running A/C and adding a set of high output head lights could be enough to burn something.
Too much draw of electrical power heats up poor connections and thin wires, exactly what happened to you.
The fire wall connector is known to be a weak point, same for the amp gauge...possible root causes of burnt connections/fire in worse case scenario.
All electrical wiring is new, does not mean it is good but lets assume these things are tested before leaving the factory.
Did you add any big power consumers? (stereo, high power head lights, etc)

No big power consumers other than I had blower motor running at the time I noticed the car was not charging.
Im thinking now based on the only damage I see is the system over charged due to a defect in the voltage regulator .
I think the voltage regulator (electronic) shorted out and created a slight ground. This is why I see a slight ground at the positive wire that supplies voltage to positive side of the coil.
At the bulkhead connection of the black wire off the alternator there was also signs of high heat, in fact it melted the foam inside the plug.
Im going to eliminate that weak point also....

 

[Wietse]

Over charge will not burn wiring, only the battery cannot stand much more then 15V.
The voltage regulator only controls voltage, thats it.
I am quite sure the slight ground you are measuring is because of the coil itself.
A ground against the positive side of the coil will create fireworks.

You said measuring at the battery you confirmed it is not charging, so what about at the alternator itself?
Is that showing 14+ volts? If it does there is a massive resistance, probably in the bulkhead connection area as there are signs of overheating.
This in effect causes a voltage drop and could be the reason why there is low voltage at the battery.