Bulkhead connector

[Fury440]

And that right there is the reason that everybody here should do the amp gauge bypass mod....

That's not really true, the ammeter has nothing to do with a smoked bulkhead connector. The bulkhead connector meltdown is 100% a result of a loose, dirty, high resistance joint. Here is my bulkhead connector.

I moved the connectors to the still good adjacent empty slot. My ammeter is still in place. It took many years of neglect to burn that slot #16, but I've learned from that and will keep the connections clean. Problem solved.

 

[sportsuburban]

High resistance coupled with high amperage is a disaster waiting to happen. Even under the best conditions and cleanest connections the amperage in this circuit can easily exceed the rating for the wire gauge and Packard 56 connectors. Add modern accessories and a modern high output alternator and things go bad fast.

For me, I've got too much time and money invested in my cars to risk the " today it decided to melt down" thing. Ammeters are eliminated and all high amp circuits are on relays.

 

[Fury440]

High resistance coupled with high amperage is a disaster waiting to happen.

Sort of true, in our case any resistance at a joint produces heat and this heat further loosens the connection. This introduces more resistance and more heat. Eventually things start to melt and could start a fire.

Even under the best conditions and cleanest connections the amperage in this circuit can easily exceed the rating for the wire gauge and Packard 56 connectors.

No, the circuit is protected by a fusible link. The wire, #10 and the connectors are rated for the fusible link amperage. The meltdown problem is not due to high current, it's due to localized hot spots at dirty connections. Adding a ton of new toys will not meltdown the bulkhead but will probably blow the fusible link.

Add modern accessories and a modern high output alternator and things go bad fast.

This is very true, you simply can't much load to any 40 year old car's electrical system. Those old systems were usually configured for a 37 amp alternator and the wiring gauge was just large enough to handle optional equipment of the day. Bolt in a 100 amp alternator without adjustments to the wiring will bite you. Bolting in modern high power draw toys will overload everything unless you use relays for power.

Ammeters are eliminated and all high amp circuits are on relays.

Ammeters get blamed for everything. An ammeter is really a voltmeter measuring the voltage drop across a small shunt. Where the problems arise are the two terminals which uses nuts to attach the wiring to two studs. If one of the nuts gets loose, you get resistance and heat which then makes the nut looser. This causes meltdowns. How do the nuts get loose? Joe owner decides to install some toy and is pulling dash wires this way and that to do his install. Pulling the harness connected to a stud will loosen the nut.

 

[sportsuburban]

No, the circuit is protected by a fusible link. The wire, #10 and the connectors are rated for the fusible link amperage. The meltdown problem is not due to high current, it's due to localized hot spots at dirty connections. Adding a ton of new toys will not meltdown the bulkhead but will probably blow the fusible link.

Well, yes there is a fusible link. Yes it can blow. But as you say, even this is probably. I pulled a totally melted dash harness out once that had a just fine fusible link but many bare wires under the dash. Thing was melted in a solid mass. How it never burned I just don't know. Actully melted to a heater duct.

Too risky for me with 50 year old wire and insulation that is breaking down.

New GXL wire all round for me.

 

[Fury440]

All that is due to hot connections which eventually heat soak and melt their way back thru the harness. If you are lucky and the melted blob makes a dead short, fuses and probably the fusible link will blow. Unfortunately a hot wire that doesn't carry enough current to blow a fuse will quietly do it's thing liked a ticking bomb.
Three areas to really pay attention to, the nuts on the ammeter, the connections on the headlight switch and the sneaky bad boy, the floor mounted hi/lo beam selector. That switch is mounted in a potentially wet/dirty location and nobody ever checks it until it stops working.
There are relay kits that plug into your existing headlight harness and connect to the battery such that your dash and floor controls no longer carry any headlight load. These are cheap and they nicely eliminate two bad spots. The ammeter problem; use star washers above and below the wiring eyelets, make the nut tight, then add a second lock nut and make it tight. Pull on the wires and if you get "any" movement, start over again. With those two fixes you are pretty well good to go.

 

[sportsuburban]

Maybe I'm paranoid but I've seen several good electrical fires over the years. One destroyed a snowmobile and gave my dad some nasty burns. Another was a brand new skidsteer loader I was driving that had a pinched hot lead from the factory. Cut the positive cable right off the battery with my pruning shears to stop it. Another was 480v arc flash and that was, well, insane.

So, I replace, improve, double nut, over insulate, over fuse everything. All wire is oversized.

And yes, everything is on relays.

Most problems could be avoided if people would only inspect this stuff. Cleaning and tightening go a long way on a stock setup.

 

[Fury440]

Most problems could be avoided if people would only inspect this stuff. Cleaning and tightening go a long way on a stock setup.

Amen to that!

 

[mr. fix it]

Back when the Hyundai Pony cars first showed up they were cooking wiring harnesses from the get go.
I was paid very well to replace harnesses under warranty when i worked for that dealership..
If I recall correctly they used a 20g wire bundle

 

[Fury440]

Back when the Hyundai Pony cars first showed up they were cooking wiring harnesses from the get go.
I was paid very well to replace harnesses under warranty when i worked for that dealership..
If I recall correctly they used a 20g wire bundle

I think the smallest in Mopar was #18, many runs are #16 and some are #14. The heavy power were all #10. There is very little room for additional load from toys on any of these circuits. To save a bunch of relays, a good solution is to run a #8 or #6 bus from the battery to a secondary fuse block under the dash. Protect the bus with a properly sized fusible link. Then all your toys can be fed from the fuse block. I'd still relay the headlights.

 

[mr. fix it]

I think the smallest in Mopar was #18, many runs are #16 and some are #14. The heavy power were all #10. There is very little room for additional load from toys on any of these circuits. To save a bunch of relays, a good solution is to run a #8 or #6 bus from the battery to a secondary fuse block under the dash. Protect the bus with a properly sized fusible link. Then all your toys can be fed from the fuse block. I'd still relay the headlights.

I am in the process of re-engineering my body harness and is is mostly 18g, some 16g and a few as low as 12g for the convertible top circuit.
I plan to post up pictures of the harness later tomorrow since this is when I am building it!

 

[Fury440]

I am in the process of re-engineering my body harness and is is mostly 18g, some 16g and a few as low as 12g for the convertible top circuit.
I plan to post up pictures of the harness later tomorrow since this is when I am building it!

Go thicker by 2 gauge steps, ie if Ma Mopar used #18, you use #16, etc. Note the normally available gauge is always an even number. Use a wire table to know what loads wires will handle, surge, steady load, wrapped and unwrapped. When in doubt always go thicker.
You need to be careful to properly support the harness, if it can move or bounce around wires will fatigue and form hot spots. Wrap only enough to support not to insulate and trap heat. Use good quality commercial grade crimp on wire ends and pay the $100 to get the proper compression pliers.
You don't want to do this twice!
Do not solder any connections, hot solder wicks up the stranded wire to form a rigid section prone to fatigue and degrades to insulation which will micro crack and allow moisture into the wire core. If done right, a wiring harness is a work of art, if corners are cut the harness will be your worst enemy!

 

[live4theking]

Big_John thanks for the education. I called the deox grease, probably because that's what it looks like, but it's always best to refer to something correctly.

I got my bulkhead connector apart and found that there was no corrosion or signs of it getting hot. What a blessing. I've got some pictures I snapped of it too, just not accessible right now.

BTW, I don't know if 68 bulk head connectors are different, but mine had catches on the sides that needed released to get the connector apart.