I have been having a discussion with a bunch of the people I know who know something about electrical circuits. A couple of things has come up. One of them is the issue that parallel circuits tend to have LOWER resistance than the sum of
each individual circuit. This is a good thing if one runs a parallel wire to each of the number 12 factory wires rather than just replacing them. The downside is that if you fuse both the old and the new you risk the possibility of allowing way too much current
through the wires if there is a shot. They confirmed what I thought on this.
I agree with everyone that talked about the importance of all the connections to be Clean, Dry, tight and Deoxidized. I go through those little $30 cans of DeOx on a regular basis.
Assuming all the above, I think that my preferred solution is not a bad one. Take the two #12 wires out of the bulkhead connector and run them through a mega fuse holder and pick a fuse with the correct current and time delay for the protection
needed. Those calculations my take me a few days. I have to read up as it has been decades since I studied that in detail. The new #10 wires will be installed with relays fed from the factory #12 wires. I could place fuses in the #10 wires as long as they
are before the relays. That would guarantee against any issues.
The one thing that was pointed out to me was that if I wanted to provide a path around the AMP meter is that I could jump my #10 wire from the Alternator to the Starter Relay Battery Stud and so if the battery needed to draw a lot from
my PowerMaster 90 Amp alternator it would provide another path. I just need to fuse the jumper as well.
I know this seems like over kill. But, since getting NEW 35 AMP alternators is tough and I want that 40 or so AMP at idle and stop and go traffic in the rain, at night, with everything going….
The real issue will be making a block that I can mount on the drivers side fender that would hold neatly the fuses and the relays.
James
From: Rich Barber <c300@xxxxxxx>
Sent: Wednesday, November 16, 2022 17:04
To: James Douglas <jdd@xxxxxxxxxx>; 'Chrysler 300 List Server' <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: RE: {Chrysler 300} Bulkhead Wires, over heating issues, typical of 1960's MOPAR -Wonky technical discussion.
There has been some thoughtful dialog on this subject and I hope this adds to the knowledge/experience base. During the restoration of our 300K conv with air, my technician
was working on the RH door power window with the engine off. Smelling smoke, he quickly disconnected the battery but discovered the bulkhead connector had melted around the area where the #12 wire from the battery passed through the bulkhead connector and
allowed the hot wire (!) to short out to several other wires. My perception was that as the battery Voltage dropped, the current needed to operate the P/W motor increased and that current/power for the most of the car’s electrical load normally came through
the bulkhead connector on the wire from the alternator and when the engine was running. Further, the 30 Amp circuit breaker that protects the power seats, power windows and power top did not open so the current was probably under 30 Amps. The problem arose,
partially due to a poor connection at the bulkhead connection on the hot wire from the battery.
Lessons learned Inspect the bulkhead connections by removing the two 8-wire connectors from the bulkhead connector under the hood. Clean and polish any corroded/oxidized connectors,
especially the two #12 connections of the #12 feed wires (black & red). Do not operate the power top, power windows or power seats with the engine off.
Whilst shopping for a replacement bulkhead connector it appears the similar ’63 Chryslers ran these two #12 feed wires into the ammeter via a copper bar through the plastic
with screw terminals for ring connectors at least on the engine side. The ’64 wiring diagram indicates a 40-Amp fusible link was an option—likely for police & taxi service. I don’t see this adding much protection for an under-designed bulkhead connector
with the same Packard connectors for 20-30-Amp service as the much smaller loads for lights, ignition, horn relay, washer pump, compressor clutch loads under the hood. I don’t see that A/C adds that much load, but mebbe so. BTW, anyone ever seen a ’64 Enforcer
police car? Or a ’64 Chrysler taxi???
A conservative fix would be to get current in and out of the passenger compartment via an alternate route. I like the idea of soldered connectors passing through separate and
nicely. grommeted new holes in the firewall. Maybe pass fusible links through the firewall and solder in each end. Lacking soldering, add a short terminal strip with ring connectors on one or both ends.
And, yes, most MoPars of this age do not experience this issue—but it is too common of a problem to ignore. Nowadays it might justify a recall.
Be careful out there. Keep these beasts alive.
Rich Barber
Brentwood, CA
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?
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