{Chrysler 300} Bulkhead Wires, over heating issues, typical of 1960's MO

Hi All,

I have been reading up on the issues with bulkhead wires melting down. My old 1964 300K CV had that issue when I purchased it and it did not have A/C.

There are several different approaches to the issue. I have read over several of them on the internet. I have also talked to a friend who is EE.

I am interested in a nondestructive approach that would deal with the issue. This car has AC and will be driven daily in the Central Valley of California and at our place in San Francisco a 1000 yards from the pacific as well as cross country this spring and summer.

What I am thinking of doing, and if you are not very familiar with electrical theory then just close this message, is to add two load bypass wires; a shunt of a sort.

The problem with just adding a couple of wires run through the firewall, like Chrysler did on the police version of the cars, is that if something draws a big load the factory #12 wires could still melt in the bulkhead connector.

My idea is to add a #10 wire to each side of the AMP meter. One would run to the BATT side of the Alternator just like the factory wires does and one to the starter relay just like the factory wire does. For 1964 that would be the R-6 wire and the A-1 wires. My wires would parallel the factory wires.

Now the issue is how to protect both the existing bulkhead wires and all the other harness wires in the event that something draws too much current through those new #10 wires. You cannot fuse both sets of wire as that would almost double the available current to say something like the AC or headlights.

What I am proposing is to pull the two existing #12 wires out of the bulkhead connector on the engine side. Then route each one with a short wire to a MAX Fuse block. Then route them back to the original mating bulkhead connector. Then on the protected side of the MAX fuse block, run a hot feed to a high current 12 volt relay. That relay would control when and if the new #10 wires were in circuit. If the fuse goes it would cut the power not only on the factory #12 wire, but would open the #10 wires via the relay as well.

Such an arrangement would be totally reversable and not cause any cutting into the harness. I would have to play with the fuse size. Those factory #12 wires theoretically are only rated for about 30 AMPS. The factory alternators were 30 to 50 AMP. Not good especially with that crappy bulkhead connector.

I suspect I will have to start at about 40 AMPs and see what I get on a rainy night with the AC on to defrost, the headlights on high, the fan on high, the rear defroster fan running, the radio on and the like.

Any Electrical Engineers on the list who want to chime in?

James

{Chrysler 300} Bulkhead Wires, over heating issues, typical of 1960's MOPAR -Wonky technical discussion.