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

xcookpac

Greasemonkey
Mar 15, 2012
144
28
I am in the beginning stages of fabricating a new harness from the bulkhead connector to the engine for my 1985 El Camino. I thought that I would document the process here. My 1985 EC has the following equipment attributes (which need to be considered for this wiring project:

1. factory gauges for volts, coolant temperature and oil pressure;

2. I want to also run idiot lights for coolant temperature and oil pressure (my recollection is that the gauges had no idiot light backups);

3. I am running a Mountain Man built Quadrajet carburetor;

4. I will be running the electric choke and idle solenoid (which kicks in when A/C is turned-on);

5. The original SI alternator has been replaced with a CS alternator. I purchased a SI-to-CS alternator adapter (however, I will likely cut the one end off and just solder into the new harness);

6. I will be retaining the original oil-pressure switch in the choke circuit;

7. I have installed a ford solenoid adjacent to the battery (on the passenger side);

8. Fusible links will be run from the ford solenoid (mentioned above in point #7);

9. I will be running A/C on my EC;

10. I have installed a power distribution junction block on the firewall; and

11. I intend to run relays for the idle stop solenoid and the choke (this way the voltage can be routed through the relay from the power distribution junction block).
 

xcookpac

Greasemonkey
Thread starter
Mar 15, 2012
144
28
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.
1985_EC_wiring_excerpt_revised.JPG
 

xcookpac

Greasemonkey
Thread starter
Mar 15, 2012
144
28
QUOTE="xcookpac, post: 786711, member: 12034"]
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?

[/QUOTE]


See: https://www.rapidtables.com/calc/wire/wire-gauge-chart.html

9 gauge is the closest to 3.0mm. Could be. But 9 Gauge is an unusual size (does not mean that GM did not spec it that way).

1592315077484.png
 
Last edited:

UC645

G-Body Guru
Apr 20, 2020
648
93
Kittanning, Pa
12 gauge is around 4.8mm (.189 thousandths) if my charts are correct.
10 gauge is a little above 4.9mm.
It was just a guess, but Ima say there's more than .1mm difference between 10 and 12ga....

Yeah... that info on my end is utterly redundant to what X is looking for. Gotta read things twice before I post from now on.
GXL might refer to the type of wire coating GM used, give me a minute and I’ll check a few places.
 
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xcookpac

Greasemonkey
Thread starter
Mar 15, 2012
144
28
Yeah... that info on my end is utterly redundant to what X is looking for. Gotta read things twice before I post from now on.
GXL might refer to the type of wire coating GM used, give me a minute and I’ll check a few places.


My understanding is that GXL wire is high temp multi strand wiring. For more complete and thorough definition see: https://www.awcwire.com/productspec.aspx?id=type-gxl
 
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UC645

G-Body Guru
Apr 20, 2020
648
93
Kittanning, Pa
Yeah... that info on my end is utterly redundant to what X is looking for. Gotta read things twice before I post from now on.
GXL might refer to the type of wire coating GM used, give me a minute and I’ll check a few places.
It is in fact referring to the type of coating applied to the wire

If you’ve got the pockets, use SXL wire, the coating is thicker and it should have higher oil resistance.
 

motorheadmike

Geezer
Nov 18, 2009
6,152
113
Ottawa, Ontario Canada
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