Simple Bulkhead Bypass

cbarge

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I had been asked by a few members to do a simple step by step of this poplular upgrade.
People have a tendacy to read into electrical too much and some of our newbies can be overwhelmed by in depth explanations involving OHM,amps or Thomas Edison.
So I will keep this simple and in laymans terms.

This mod will help keep your 40 or 50 plus year old C on the road.
The bulkhead connector is the thingy on the firewall with all the wires that go into it.
Including the main battery power that feeds everything that goes into the car.
When that shorts out it is like using an electric mower but ran over the extension cord that powers it.
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cbarge

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Disconnect battery.
At the starter relay using a fusible link or inline fuse ( your choice but link is my preference) run a wire towards the firewall.
I like using 10 gauge wire with a fusible link 2 sizes smaller.
20200611_213427.jpg

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cbarge

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Run wire through firewall.
You can use the speedo cable grommet or make a new hole using a new grommet, and make sure the wire does not touch any sharp edges or metal.
Note that I kept the factory fusible link at the bulkhead intact.
It can be removed but I left mine alone..
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cbarge

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From inside...
Wire is going to ammeter gauge in the instrument cluster.
20200611_213532.jpg
 

cbarge

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Depending on your car,you may have to pull the gauge cluster out for this next step.
Refer to your car's Shop manual for cluster removal.
Or be adventurous and work upside down if you have small hands.

Connect the wire to the RED terminal of the ammeter gauge.
boab august 2017 015.JPG

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cbarge

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Button up the dash knowing you have made your car that much more reliable and fun to drive.
Oh and dont forget to connect the battery,LOL!!
Cheers and let the questions fly!!
boab 2018 007.JPG
 

jct

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How did you remove your gauge cluster without lowering/dropping the steering column?
 

cbarge

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How did you remove your gauge cluster without lowering/dropping the steering column?
I did remove the three bolts from the upper portion of the column.
You just dont see it in the pic.
It was enough to pull down on the column to clear the cluster.
I cheated.
Other cars you must to undo the bolts at the base of the column at firewall.
As mentioned,refer to your car's shop manual for your particular car.
 

73Coupe

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Thanks for the detailed photos and description. So basically this bypasses the bulkhead connector that is prone to corrosion because of its semi-exposed location....

It's still important to inspect the rest of the connectors and pack them with grease.

For the C bodies with the earlier style electrical system, where all the battery power passes through the ammeter, isn't the ammeter and its connections on the back considered an Achilles hell as well? Later cars like mine used a shunt setup.
 

Ross Wooldridge

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This is great Leaburn, and thank you!! And for fun, I responded last night immediately upon you saying for us NOT to post until you were done just to piss you off!! LOL!! :lol::canada:

Question - while your modification removes a very large amount of the constant high amperage power running through the bulkhead from the engine bay to the ammeter, there are a few high power things that run BACK to the engine bay THROUGH the nasty old bulkhead AFTER the ammeter and the welded splice in the dash harness (headlights, AC compressor, etc etc). To make this a true Bulkhead Bypass, can these return power feeds not be run through the firewall as well avoiding the pesky spade connectors in the bulkhead? Maybe using insulated terminal blocks for serviceability? (see below)... would that not reduce the bulkhead overload issue that can exist with those circuits by doing that as well?

Observation: My 66 Monaco has the police style power delivery system which used a bulkhead bypass almost exactly as described, but rather than running an unbroken wire from the starter relay through the firewall to the ammeter, it runs it to a nice insulated terminal block bolted to the firewall, and then through the firewall in its own special hole to the ammeter. In this case the starter relay is on the firewall (rather than the inner fender like your car), and the factory used a fusible link (red with a white stripe) run directly from the relay terminal to the insulated terminal block (upper left just below the hood spring bar), then a new red ammeter feed wire going down to a hole in the firewall with a grommet (you can't see the hole, but you can see the feed wire - it's the vertical red wire). As you stated, they also retain the fusible link from the bulkhead, so you can see the two yellow fusible link plastic identifiers on the starter relay bolt. This allows for some serviceability - see the photo below. In my car this is where the voltage regulator would be, but in some police cases (and I've seen this on Imperials too), the voltage regulator is mounted on a special bracket on the inner fender, and the wiring harness is modified with a jumper wire from an additional terminal block from the regular harness to the regulator on the inner fender. You can see the second terminal block below the red and white fusible link wire.

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IMG_0446.JPG
 

Gerald Morris

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Guys. ANY conductor which you don't want to entrust to that bulkhead connector can be routed straight through. You can do this by 1:) Carefully drilling out the clips in the bulhead connector, then using a soldering iron to smoothly burn away the remaining plastic shards to make a neat, insulated hole to pass a SMALL GAUGE (#16-20 AWG) wire through, or 2.) Get a rubber grommet into a nearby hole in the firewall, and pass your larger conductors through that. Replace anything that formerly connected to the bulkhead connector with straight wire passing through. This eliminates the junction subject to dysfunction there.

I've replaced 3 or 4 of my crucial conductors thus, and have no electrical worries, nor have had any but the wonky fuse box clip for interior lighting in 3 yrs. This stuff is too easy to deliberate over, IFF DONE RIGHT!
 

Clover

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This is great Leaburn, and thank you!! And for fun, I responded last night immediately upon you saying for us NOT to post until you were done just to piss you off!! LOL!! :lol::canada:

Question - while your modification removes a very large amount of the constant high amperage power running through the bulkhead from the engine bay to the ammeter, there are a few high power things that run BACK to the engine bay THROUGH the nasty old bulkhead AFTER the ammeter and the welded splice in the dash harness (headlights, AC compressor, etc etc). To make this a true Bulkhead Bypass, can these return power feeds not be run through the firewall as well avoiding the pesky spade connectors in the bulkhead? Maybe using insulated terminal blocks for serviceability? (see below)... would that not reduce the bulkhead overload issue that can exist with those circuits by doing that as well?

Observation: My 66 Monaco has the police style power delivery system which used a bulkhead bypass almost exactly as described, but rather than running an unbroken wire from the starter relay through the firewall to the ammeter, it runs it to a nice insulated terminal block bolted to the firewall, and then through the firewall in its own special hole to the ammeter. In this case the starter relay is on the firewall (rather than the inner fender like your car), and the factory used a fusible link (red with a white stripe) run directly from the relay terminal to the insulated terminal block (upper left just below the hood spring bar), then a new red ammeter feed wire going down to a hole in the firewall with a grommet (you can't see the hole, but you can see the feed wire - it's the vertical red wire). As you stated, they also retain the fusible link from the bulkhead, so you can see the two yellow fusible link plastic identifiers on the starter relay bolt. This allows for some serviceability - see the photo below. In my car this is where the voltage regulator would be, but in some police cases (and I've seen this on Imperials too), the voltage regulator is mounted on a special bracket on the inner fender, and the wiring harness is modified with a jumper wire from an additional terminal block from the regular harness to the regulator on the inner fender. You can see the second terminal block below the red and white fusible link wire.

View attachment 382062
View attachment 382066
It’s interesting To see that Ma Mopar knew that the bulkhead connector wasn’t really adequate from at least 1966!
 
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