Wiring Help - 1972 C10 Big Block

[Gibby56]

Hey guys, I’m working on a 72 C10 and am getting confused over some engine wiring. I bought all new reproduction OEM style harnesses for this thing and am having issues figuring out what the wires below go to.

The harness itself is for a big block, HEI, auto transmission, and the alternator on the driver side.

Picture of my mystery plugs are below. They are in the engine harness and are all bundled together. The colors of the wires don’t match the schematic I’ve found posted online.

The blue wire looks like an oil pressure which doesn’t make sense since these have mechanical gauges

The green wire looks like TCS or water temp.

I have no idea what the big pink wire is for. I have the correct one hooked up to the distributor.

Any of you guys know?

 

[500$k5]

Is it a TH400 truck. Green might be kickdown, for the trans

 

[Gibby56]

The left reddish pink should be the height power, keyed hot. Middle blue is oil pressure, pretty sure. The green should be a/c related

No AC on this truck and that harness is a different PN. I’ll check the big pink with a battery and a volt meter. If that’s the case, i can use it for the electric choke.

Is it a TH400 truck. Green might be kickdown, for the trans

It’s a TH350

 

[Wes Harden]

I didn't read your whole post well so my answer was miss informed pls disregard

 

[6872xtc]

I thought that all of the big blocks got a TH400 in those trucks. But I thought that the kick-down harness had orange and black wires anyway.
I have seen idle step-up solenoids or anti-dieseling solenoid using a dark green wire, but just a single wire.

The oil pressure wire doesn't make sense, as you said.

I don't remember seeing a large pink wire with that connector on the engine. The coil power should have a fork terminal. But I have never seen HEI in a '72, so maybe they got that terminal incorrect?

 

[Gibby56]

I thought that all of the big blocks got a TH400 in those trucks. But I thought that the kick-down harness had orange and black wires anyway.
I have seen idle step-up solenoids or anti-dieseling solenoid using a dark green wire, but just a single wire.

The oil pressure wire doesn't make sense, as you said.

I don't remember seeing a large pink wire with that connector on the engine. The coil power should have a fork terminal. But I have never seen HEI in a '72, so maybe they got that terminal incorrect?

You’re totally right, big blocks did come with 400’s. This truck originally had an I6 and a SM465. I swapped in a 496 from my Chevelle and a built TH350 I got from a buddy.

I bought every new harness LMC offers and things just seem weird. The wire for the HEI did have the special “clip” connector that holds it into place. That one is hard to mess up, at least I hope haha.

I have done some reading and some of these harnesses come with options that might be universal. For example, my truck has all the gauges but this harness has the plug for the oil pressure idiot light.

I think I’m going to hook up a battery and just start having fun with a volt meter and some resistors.

 

[Gibby56]

Just for fun. Here’s what I started with and here’s where I’m at.

Its an original short bed with the original ochre paint (white is just sprayed over the ochre)

 

[6872xtc]

Cool build! Where did you find that steering wheel? That's the exact one I was wanting for my '72, but I didn't find it in that diameter. I ended up getting a 14" one, but I don't really like the small size in a truck.

 

[Gibby56]

It’s a reproduction of the optional steering wheel from a 1970 Chevelle. I really dig it.

 

[Gibby56]

Went to Goodguys today. I found an original big block truck. Looks like the green wire is definitely the temp sensor, the blue is an oil pressure for the dummy light, and the large pink is still unknown. I’m hoping it’s a keyed power source like @Wes Harden said so i can use it for the electric choke.

Here’s some pictures of the reference truck. The oil pressure and the pink wire are just tucked back and taped up.



That truck is for sale ….$75k

 

[Wes Harden]

Put a test light between the green and ground turn key on see what temp gauge does. With and with our the test lamp.
One thing bugs me is the extra lead spliced into that connection.
That pinkish wire may very well be the choke coil

 

[ashman]

Default gm colors is pink = keyed power. That big pink wire should be a power lead for something.