Burnt fusible link 68 Dart

The Dart was in storage due to other issues taking my time. I went to do the monthly run and warm up, battery too low to get it to fire. So I pulled the battery and bought a replacement just to get it going, no resto correct needed here. Put the new battery in and connected the negative cable then on to the positive side. The clamp made a slight spark as I put it on the post and as I started to tighten the nut, I smelled something and then saw smoke billowing up at the firewall. I quickly pulled the cable off the battery post but inspection after the smoke cleared revealed the fusible link on the center terminal was fried. The key wasn't on, in fact not even in the car. I pulled the wiring terminal off the bulkhead connector and found just a little corrosion on that one blade for the FL. I can't find anything else from a visual inspection that looks damaged or that may have caused the FL to burn up. So what do y'all think went south? The amp gauge? the new battery? Or just a freaky coincidence?
I've ordered replacement terminal blocks for all three sections and a fusible link but am hesitant to hook it back up without something determined to cause the cause. I intend to clean up the bulkhead connector and check all the connections before trying it again. What else?
The ignition is a MSD 6al with a hidden kill switch, Accel coil and wires, but mopar distributor. About 10 years ago the instrument cluster was pulled and all connections checked, solder joints renewed.

Not a poor connection or open connection in this case
Fusible link working correctly = battery grounding.
And yours worked correctly. It melted quickly when the battery was hooked up.
Therefore something on the power circuits grounded.

Start with alternator output stud. If you have an ohmeter, disconnect the output wire from the alternator and check for continuity to ground. Check the stud, check the wire.
If its in the wire, disconnect at the bulhead and check continuity. Keep working your way back.

Without an ohmeter, you could hook up a 12 volt, low amp light. With a device in the line, that should restrict the flow. Another trick is to wire a flasher unit to act as a quick acting, resetting circuit breaker. I think that's in on of th Chrysler master Tech pamphlets. I haven't tried that myself.

Below is an example of a fusible link in action. In this case it shows a wire that has been rubbing against metal until the insulation was worn through.

Thanks Mattax, gives me a place to start. And I do have a amp/volt ohm meter.
Would a shorted starter cable take out this fusible link?

Not a short to ground. Current would flow down the big cable and you'ld see an arc welding show!


OK.
You can use the ohm meter to check for continuity to ground. One probe to the circuit and the other to a good ground. Its not directional. it has its own small power source. The car battery must be disconnected when using the ohm meter.

The ammeter portion of most multimeters can only handle very small currents. Typically miliamps. Some can handle up to15 amps for very short periods of time (less than minute). Check the instructions but this function will probably not be useful for diagnosing your short. If you had been in the drivers seat and glanced at the car's ammeter you would know whether the short was before or after the meter. Either current was flowing through it or not. I don't think we don't want to recreate that scenario again!

Voltmeter can be useful when its safe to reconnect the battery.
When the battery is hooked up, and all all switches are off, circuits are then open. Picture a knife switch.
Voltage will be present in all wires connected to the battery with no switch. These are always hot and always should be at system voltage.
Voltage only drops when current is flowing through resistance. Resistance could be a a bad connection but normally its a light bulb or motor.

All the wires attached to the main splice are always hot.

As said take both batt cables off/grab your meter/start check the circuits for continuity to ground (alt/bulkhead then inside under the dash)

Make sure the loose battery cable clamps don't touch ground or you will find continuity. LOL

Thanks, will be working on it this weekend.
Jim H.

" Put the new battery in and connected the negative cable then on to the positive side."

I am sure it is just a typo but, it reads like you "connected the negative cable then on to the positive side."

It is always recommended to connect neg cable last.

Well that's one thing That I did backwards, but I did know better.

New question, I need to replace the positive side battery cable to starter. When I stared moving wiring around the insulation on it cracked and started falling apart. I see period correct at Classic Ind. for $142 but that is not needed. Any other sourcing suggestions?

Factory cable was 6 AWG Black or Red with 10 gage red to the starter solenoid.
I prefer red as its almost universal indicator. Less mistakes.

If you have marine boating supply place, that would be my first choice for materials. Marine wire grade wire is tinned and so more corrosion resistant. Also has a higher temperature oil resistant insulation than general purpose automotive wire.
Problem is making a good crimp or solder connection on the terninal - especially with two important wires connecting there.
See what and who might be able to copy the lengths and terminal connections locally. Not cheapy clamp type either, You can do that yourself in an emergency.
If they have 4 AWG starter wire instead of 6, that's OK too. As long as the terminal connection and the wires are a match, along with the opening sizes on the ring terminals.