72 C10 Longbed Duramax Swap!

TheIronGeek

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Nov 16, 2013
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hey guys!
save me!!

ok so now i'm finally working on the ignition wiring. I'm planning on hooking it up to my stock 72 ignition switch, but i can't figure out what wire does what! i've found a couple wiring diagrams, but none of them show 7 wires like i've got. can anyone give me some insight?

the two Red wires are always hot. but beyond that i havent been able to figure them out!

Thanks!!!

Nate
 

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TheIronGeek

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Nov 16, 2013
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2005 lly

The plug in the picture is what plugs into the ACTUAL ignition switch.

to picture-ignition switch- the key assembly.


edit for clarification :)
 
Last edited:

TheIronGeek

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Nov 16, 2013
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OK guys, I'm having a little panic, and i need someone to talk me off of a ledge :)

first: when i have the 2005 ignition switch connected to all the wiring (like it should be) the truck cranked, started, and ran just fine.

second: i took apart the ignition switch (which was kinda neat) to see how it worked. Looking at the switch, and the info ty_LBZ shared with me, it LOOKS like at the ON position: pink(ign1) red(always hot) and brown(acc2) are switched together; also orange(acc1), white(ign2), red(always hot) were all switched together.

third: when you flip the switch to START the Yellow switches on with the orange, white red, and it cranks and starts.

so, in an effort to make sure this theory was correct, i fixed myself up two switches, and engaged them. crank no start.

put the stock switch back in place, crank no start.

i'm having a moment of panic, worried that because i had them all switched "on" while it was cranking that i blew something....

i found a blown 20A fuse in the (i think) Aux PWR slot in the underhood fuse box. But, i don't know why that would be connected to my problem.

if anyone has any insight it would be great! ... you can also tell me i'm dumb if you have to...

thanks!
 

TheIronGeek

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Nov 16, 2013
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alright!
Figured it out!
i'm dumb! haha!

basically what happend, the day all of this started showing up, i had ALSO installed my twin kennedy lift pumps. To do that, i drained my fuel lines, and never re primed anything. so, the reason the truck wouldn't start was: i was sucking air!

thank god!

:D now that i have that hunted down, i'm good to keep rollin'!
 

036.6turbo

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Jan 17, 2014
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Awesome project. I would like to put my LB7 in a 65 C10 LB someday.

For now I'll follow along with you!
 

TheIronGeek

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Nov 16, 2013
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Joyous news!

I finally started the truck with the 72 switches! It looks like we have everything worked out!

so, i don't have an actual diagram, but i'll give the lowdown here, for anyone that is looking for the info... the way that i've spent the last few weeks trying to figure it out!

2005 Duramax LLY Ignition Wiring

full disclosure, i have the full "in cab" 2005 harness AND the full 72 harness in my truck also. I'm sure some of you more experienced fellas could have done this more elegantly, and with less wiring :) but i'm still learning!

I took the 2005 Ignition switch apart, and it looks like in

Position 1(accessory): Pink (ignition1) and Red (always hot) are engaged

Position 2(run): Pink(ignition1), Red(alwayshot), White(ignition2), Orange(accessory/Heaterblower1),Brown, Red(a second alwayshot)

Position 3(start): red(always hot) Yellow(Starter) Pink(ignition1) White(ignition2)

So, while i was testing to figure out what actually needed to be hooked up to make it start and run. I fashioned 2 switches.
One toggle: Red(always hot) and on the other post i had Pink(ignition1) and White(ignition2)
Pushbutton switch:Red(always hot) Yellow(starter)

It started and ran! So, bare bones start and run works!

Now, to marry it to my 72 switch and harness!

Basically, i wired the 2005 ignition wires (Ignition1, and Ignition 2) to the 1972 Ignition Coil Wires (i had to run them back through the firewall). and the 2005 Yellow(starter) wire to the 1972 Purple(starter) wires.

finally started right up! If you guys have any questions about it, or i've been unclear ( super possible :) ) Let me know and i'll try to streamline this some!
 

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