Fabricating New Harness from C100 Bulkhead Connector to Engine, A/C, Etc.

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pagrunt

Geezer
Sep 14, 2014
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Elderton, Pa
In the GM schematic, the conductors for power supply to the bulkhead (AKA C100) is specified as 3.0 GXL. My real life experience tells me that this should be 12 gauge GXL wire (or perhaps 10 gauge wire). Does anyone have any better explanation of the 3.0 designation by GM for what most would call 12 gauge wire?

PS See attached pic. Pink 3.0 GXL is the conductor for the HEI ignition. View attachment 149211
Due to the attempt to put the US on the metric system in the late '70's alot of companies converted everything they could to metric. So woth the 3.0 wire gauge is equal to 12 AWG. In all my Chevy manuals with wire diagrams have a conversion chart for metric to AWG. Nice to see someone else taking the challange to do this kind of wire work.
 
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88AZSS

Master Mechanic
Mar 13, 2018
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You mentioned having full gauges and also wanting to cut the leads for the CS alternator to use the CS plug only. If you do do this, don’t forget to leave the resistor that’s should be soldered in to your adaptor harness. It is necessary when using full gauges and running the upgraded alternator. I just did this upgrade myself recently and from my research into it, I’ve read doing without the resistor when having gauges causes issues with charging.
 
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xcookpac

Master Mechanic
Mar 15, 2012
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full gauges and running the upgraded alternator. I just did this upgrade myself recently and from my research into it, I’ve read doing without the resistor when having gauges causes issues with charging.
Many thanks for the heads up. Tips like yours are one of the many reasons that I post projects up here. There is a lot of knowledge here. Many thanks!!!
 
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UC645

Royal Smart Person
Apr 20, 2020
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Many thanks for the heads up. Tips like yours are one of the many reasons that I post projects up here. There is a lot of knowledge here. Many thanks!!!
If you don’t mind a bit of extra parts, you can keep your stock wiring with this adapter:

Dont forget to check your 12v reference wire for your alternator when you do this, I almost burnt my 144 up because I wasn’t getting anything out of the factory wire.
 

oldsofb

Royal Smart Person
Supporting Member
Dec 7, 2007
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Want to do some mods to my harness as well. I'll be watching this for sure :popcorn:

Hutch
 

88AZSS

Master Mechanic
Mar 13, 2018
433
1,091
93
Mesa, AZ
If you don’t mind a bit of extra parts, you can keep your stock wiring with this adapter:

Dont forget to check your 12v reference wire for your alternator when you do this, I almost burnt my 144 up because I wasn’t getting anything out of the factory wire.

Yup this is the exact adaptor harness I used. Note the resistor in line with the yellow wire. That's necessary for the full gauges. I ran the adaptor between my stock harness and new alternator but if youre looking to clean it up a bit that's a good way to go. I got mine from RockAuto for a little less but if NAPA has it in stock it may be worth it to you if you need it same day.
 

Texas82GP

Just-a-worm
Apr 3, 2015
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Tuned in. I'm doing similar. My bulkhead connector had the hardened "sealer" all over it since the car was a diesel so I took the easy and expensive way out and bought a reproduction harness to start with. I'll customize it from there. I'm running the Camaro serpentine FEAD so my compressor and alternator are swapped from stock. I'm also going to add a Ford solenoid near the battery.
 
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