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



Hi Danny, I have read over most of the “solutions” to this issue. The direct #10 wire with fuse or link is one solution but it does not protect that bulkhead connector. Again, a #12 wire is only rated at about 30 AMP’s. Add the resistance by the Packard connectors at the bulkhead and it is less. The question is if you load shed the battery recharging via a single bypass #10 wire and something in the cockpit happens to draw a high load that bulkhead connector can still burn.

 

In addition, when you bypass the AMP gauge, you then loose it as a reliable indictor of the current draw of the system.

 

I did happen to talk with one friend who is an EE, although he works at the atomic level with voltage so low as to be ridiculous at Intel. His take was that one would want a definitive fuse solution that protects that connector.

 

I know my idea is “a little complicated” but it is also very straight forward. Fuse the smaller wire and relay the larger one off of it.

 

Do keep in mind one thing. When you stated that, “to take the charging current out of the harness.” That does not really happen. In the event that the new #10 wire for some reason had an issue, like a large current spike due to a short or regulator failure and the fuse were to blow, the current would still flow through the bulkhead and would simultaneously fry it as well.

 

To make the bypass idea work AND protect the harness, cutting up the harness and re-routing would be required. There are threads out there on doing this as one can find on the MAD website.   Also, the AMP gauge would be worthless, and it would have to be converted to a volt meter. I do not want to cut up the wiring. Additions that can be easily rolled back are fine.

 

Fusing the #12 wires and relaying the #10 would provide full protection to the wiring harness both to and from the dash. If implemented on a small mounting bracket and placed on the inner fender on the drivers side, the re-route could be done with minimal fuss with the fuses and relays mounted on that single bracket.

 

Unless that is, I am missing something which is always possible --- Always very possible 😊

 

James

 

PS Caroll, I did read that link and many more.

 

From: Dan Plotkin <dplotkin@xxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, November 16, 2022 6:51 AM
To: James Douglas <jdd@xxxxxxxxxx>
Cc: 'Chrysler 300 Club International' <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: RE: {Chrysler 300} Bulkhead Wires, over heating issues, typical of 1960's MOPAR -Wonky technical discussion.

 

Jim-

I think John Grady will be along. I’m no EE. Subject to what John says I say you are chasing far too much complication. Among troubles I’ve seen along these lines is when a high capacity alternator is installed, a fresh healthy battery is installed and allowed to go stone dead after leaving lights on. When the car is jumped and that dead battery begins sucking up current the big alternator is only too happy to provide the wiring is overloaded. I smoked an ammeter on a 68 New Yorker just that way.

 

I think all one needs to do is strap a fused #10 between the alternator lug and the starter relay to take the charging current out of the harness.

 

Danny Plotkin

 

From: 'James Douglas' via Chrysler 300 Club International [mailto:chrysler-300-club-international@xxxxxxxxxxxxxxxx]
Sent: Tuesday, November 15, 2022 9:57 PM
To: Chrysler 300 List Server (chrysler-300-club-international@xxxxxxxxxxxxxxxx) <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: {Chrysler 300} Bulkhead Wires, over heating issues, typical of 1960's MOPAR -Wonky technical discussion.

 

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

 

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