Author Topic: Firewall Connector Wiring  (Read 11555 times)

Online ccz145a

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Firewall Connector Wiring
« on: October 29, 2007, 01:45:54 PM »
Swapping '84 diesel cab to '75 frame with 454 and th400.
Engine harness: 1975 big block
Fuse Block and Cab Firewall Connector: 1984 diesel.

Wiring coming out of the connector looks like someone tried to convert to a gas engine harness (Do not know if this was successful since the truck had no engine or trans when I got it and one tank still has diesel in it)

I was able to move most of the wires from my old engine harness to the "appropriate" location on the new connector.

I now just have two wires from my old engine harness that I do not know where to plug them into the new cab connector at the firewall.

One of them is the from the temp sensor on the left cyl.head.
The other is black/white.

Is there such a thing as a "pin diagram" for this connector from the 2 years 1975 and 1984 that could be used figure out what goes where?

My hope is that there would be a standard c/k wiring harness for 1984 and all the diesel stuff was a few add-on circuits, just like the ac system is an add-on circuit harness.

Thanks.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline Captkaos

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Re: Firewall Connector Wiring
« Reply #1 on: October 30, 2007, 10:24:02 AM »
Where did the black/white wire go to?

Online ccz145a

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Re: Firewall Connector Wiring
« Reply #2 on: October 30, 2007, 10:39:59 AM »
Dunno, ran out of time before going camping, haven't had a chance to look since. It had a short (~1/2in) inline fuse and did not read the amperage (glass broken now). Not a big wire by any means, look like 14 or 16ga.

Hey, you have one of those buzzer circuit probes?

Too late now, but I should have written down where the pins were on both connectors before I started. I could have started a database of this info.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline Captkaos

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Re: Firewall Connector Wiring
« Reply #3 on: October 30, 2007, 01:04:02 PM »
The black/white wire when to the junction on the firewall with a 4A fuse.  From bottom left of the connector it should be 1 over and 4 up (slot 2)


           |30 |931
B    |B  |31 |39
350| 2 |25
419| 6 |35
B    | 3 |97 |93
2    | B |92 |91


B = Blank.
30 - Pink - fuel meter
931 - Dark Blue - oil press swith
31 - tan - oil press sender
39 - not used
350 - pink/blk - oil press switch
2 - red - Alternator/splice to junction
25 - Brown - Alternator
419 - not used
6 - purple - Starter
35 - Drk Green - Coolant Temp
3 - pink - Distributor
97 - Blk/lt blue - windshied wiper park switch
93 - white - windshied wiper motor
2 - red - Alternator (2 prong plug)
92 - purple - windshied wiper
91 - Gray - windshied wiper

Online ccz145a

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Re: Firewall Connector Wiring
« Reply #4 on: October 30, 2007, 03:05:53 PM »
Thanks Chris,
I think I have that slot filled aleady. Will double check and let you know. I dont quite understand the sentence:

Quote
The black/white wire when to the junction on the firewall with a 4A fuse.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Online ccz145a

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Re: Firewall Connector Wiring
« Reply #5 on: October 30, 2007, 03:37:39 PM »
ahhh, you meant "went" not "when".

I think I have a fat red wire in that number 2 slot and the other number 2 slot as well. I had a moment (brain damaged moment, that is), and have already taken the blk/wht wire out of the other socket (the '75 model) so I am left the option of probing. If it does trace back to the hot junction block top-middle of the firewall, then I may not even need this wire anymore.

BTW, The '75 model coolant-temp wire is interestingly not visibly green, but rather sheathed with asbestos.

I also have a mechanical oil presure guage, so there will be a few more wires from the '84 connector I can remove - assuming I do not have to jumper them.

Thanks for the diagram.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline Captkaos

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Re: Firewall Connector Wiring
« Reply #6 on: October 30, 2007, 09:53:41 PM »
That's what I was trying to say, you should have that ran already....

Online ccz145a

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Re: Firewall Connector Wiring
« Reply #7 on: October 31, 2007, 07:57:19 AM »
This is good news. I think this is done. Thanks for you help.

BTW, the map is inverted top to bottom.
And it represents the female side as you face the firewall

2    | B |92 |91
B    | 3 |97 |93
419| 6 |35
350| 2 |25
B    |B  |31 |39
           |30 |931
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline Captkaos

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Re: Firewall Connector Wiring
« Reply #8 on: October 31, 2007, 08:59:30 AM »
2's are the power source wires.  If you have power everywhere those go, you are set. (starter, alternator, junction)
Yeah, I realized it after the 3rd line but didn't want to copy paste so I just left it...

Online ccz145a

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Re: Firewall Connector Wiring
« Reply #9 on: October 31, 2007, 09:23:39 AM »
Ok, here it is for posterity...

The 1984 firewall connector pin map with wire descriptions all in one place:

Represents the female side as you face the firewall

2|B|92|91
B|3|97|93
419|6|35
350|2|25
B|B|31|39
|30|931

B = Blank.
30 - Pink - fuel meter
931 - Dark Blue - oil press switch
31 - tan - oil press sender
39 - not used
350 - pink/blk - oil press switch
2 - red - Alternator/splice to junction
25 - Brown - Alternator
419 - not used
6 - purple - Starter
35 - Drk Green - Coolant Temp
3 - pink - Distributor
97 - Blk/lt blue - windshied wiper park switch
93 - white - windshied wiper motor
2 - red - Alternator (2 prong plug)
92 - purple - windshied wiper
91 - Gray - windshied wiper


1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)