Very bad intermittent short

[jmustian]

I found two large wires in my dash were smoked/melted while trying to get dash lights working in my 69 300. I replaced them and a week later the car stalled and the ammeter showed discharge. I found two main wires burnt out in the fuse box. The two connections in the fuse box could not be repaired, a black and red wires that appear about 12 gauge so I bypassed the fuse box and wired in a separate 30 amp fuse holder on each wire. Everything great for anotherm week. Went out to start the car. It fired up and then the ammeter and my volt meter showed a major discharge. The fuse holder on the black wire had melted.

Question is what makes a short that large and why only occasionally? Can the ammeter be the culprit?
I'm not a whiz on electrical but I can't find any shorts. It would have to be a major short since it didn't just blow the fuse, it melted the fuse holder also.

 

[Big_John]

If I'm reading this correctly, the only two large (12 gauge) wires that are red and black are the two wires feeding the fuse block.

No white stripes (tracers) on either wire??

That means power into the block and not out of. Any chance this car has had the "ammeter bypass"? That's the only way that you could still have power to everything.

 

[jmustian]

Ammeter still hooked up and working. Seems to lose alternator, starter circuit but I'll check again

 

[jmustian]

Ammeter still hooked up and working. Seems to lose alternator, starter circuit but I'll check again

Ammeter still hooked up and working. Seems to lose alternator, starter circuit but I'll check again

I'll see which two positions in box and what they're labeled for in the fsm after church. I really suck at wiring i have the fuses temporarily connected with wire nuts while looking for the issue. It started in the dash.

 

[MoPar~Man]

Diodes in alternator are going bad.

Fusable link in engine compartment right near bulkhead connector should have blown to prevent melting items in the dash / fuse block. Check for intact and correct fusable link. Do you have a fusie? Did they replace fusable link with circuit breaker?

 

[jmustian]

Here's. What I got. As best as I can trace wiring in book.
Terminal 28 is red wire to starter relay and splits to battery on engine side. On interior side, 28 goes to ignition switch.
This is the burnt red wire.

Terminal 16 is black wire direct to alternator power output on engine side and to ignition switch on interior. This says to me ignition switch is bad.
Last time I started it, it melted black wire while cranking.

Here is picture of red wire from battery and where headlights are patched in, does not look like a fusible link to me. I did not find any thing else that looked like a fuse link.

 

[Big_John]

Here's. What I got. As best as I can trace wiring in book.
Terminal 28 is red wire to starter relay and splits to battery on engine side. On interior side, 28 goes to ignition switch.
This is the burnt red wire.

Terminal 16 is black wire direct to alternator power output on engine side and to ignition switch on interior. This says to me ignition switch is bad.
Last time I started it, it melted black wire while cranking.

Here is picture of red wire from battery and where headlights are patched in, does not look like a fusible link to me. I did not find any thing else that looked like a fuse link.

View attachment 734037

I don't have a '69 Chrysler FSM and I know there were significant changes in '70, so I don't want to use that to check the wiring diagram.

That splice isn't stock, but I think you know that. It does make me wonder what else is going on.

I can't see how the ignition switch would be the problem though. I'm thinking somehow the starter is drawing through the some other wiring. Like maybe the wiring down to the starter is compromised and the higher draw of the starter is frying the wires because it's pulling high current through the rest of the wiring. I'd look at that starter wire and connection to the starter and relay first.

 

[jmustian]

I don't have a '69 Chrysler FSM and I know there were significant changes in '70, so I don't want to use that to check the wiring diagram.

That splice isn't stock, but I think you know that. It does make me wonder what else is going on.

I can't see how the ignition switch would be the problem though. I'm thinking somehow the starter is drawing through the some other wiring. Like maybe the wiring down to the starter is compromised and the higher draw of the starter is frying the wires because it's pulling high current through the rest of the wiring. I'd look at that starter wire and connection to the starter and relay first.

Cool. Thanks.
I think the last melt was my fault, (not me!!!)

I checked starter circuit and alternator circuit and ignition switch circuit and found my temporary repairs while checking for the problem were most likely the cause. I used house wire nuts to bypass the burnt fuse box and several had come loose from the heat. I tightened them all to check again and couldn't find any issues. Nothing was getting hot. Sorry. I'll solder everything tomorrow and give it another try.
Now to find out where a leg of the back up switch isn't working. The switch works fine but only one side of the switch gets hot so no bu lights. Always something but this group is extremely helpful

 

[jmustian]

Has anyone ever changed their fuse box from glass fuses to blade fuses?