Wiring mystery - one unexplained dark green wire left from inline 6 to 350 swap

[deucecoupe]

All --

Thanks in advance for help on this. I'm reconnecting wires from a swap to a 350 in my '84 C10. This involved '86-ing' the extra smog stuff.

I verified where every wire goes, but I have one unassigned wire I can't explain.

The wire is dark green and has a push-on connector just like a water temp connector (see pic, connector a bit crispy). I traced it back to the fuse panel (20amp) labeled STOP / HAZ. I don't recall what I disconnected it from, but is was a sensor or switch on the driver's side of the inline 6 block or head. I've verified everything else.

Anybody run across this previously?

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[crazy4offroad]

Looks like the temperature sending unit wire.

 

[deucecoupe]

yes it does look like a water temp sensor plug.

I found another wire that went to a sensor in the typical place you'd find the water temp. But its not like one I'm used to seeing, it also had several vacuum tubes attached.

Maybe I misunderstand the attached pic shows if its not the water temp.

 

[Rusty Nail]

Looks important.

 

[CorvairGeek]

GM commonly used 2 temp wires on some inline engines, even with a temp gauge. The standard sending unit was wired in parallel with a temp switch with gauges. This allowed the temp switch (sometimes called the metal temp switch) to peg the gauge in the event of an overheat too. Same idea with idiot lights. Either switch could turn on the light.
My 292 had both a temp gauge sending unit and a temp switch.

 

[deucecoupe]

CorvairGeek --

Thank you very much for the insight.

 

[CorvairGeek]

CorvairGeek --

Thank you very much for the insight.

You are quite welcome. The "metal temp switches" can drive people crazy too when they malfunction. A sudden overheat gets most peoples attention, but may not be the easiest to reproduce.

 

[Grit dog]

Nothing to add other than thanks for more great knowledge @CorvairGeek.
Not having an issue with anything but I’m just old enough to remember when perplexing things like this meant reading and re reading the Chiltons manual and asking my grandpas buddy Andy who was basically auto repair Google before google existed. Idk how anyone who didn’t have an “Andy” survived!
Now you’re an Andy for 1000s of us!
Cheers man!

 

[bucket]

Nothing to add other than thanks for more great knowledge @CorvairGeek.
Not having an issue with anything but I’m just old enough to remember when perplexing things like this meant reading and re reading the Chiltons manual and asking my grandpas buddy Andy who was basically auto repair Google before google existed. Idk how anyone who didn’t have an “Andy” survived!
Now you’re an Andy for 1000s of us!
Cheers man!

Jerry is an electrical wiz-bang. His avatar picture says it all.

 

[Scott91370]

I think there is also a green wire for the a/c idle to kick the carb open a tad when a/c is switched on - if your truck has a/c.

 

[mshawn]

Temp sender on the side of the head on the drivers side. Toward the frond of the head.

 

[Grit dog]

Only single green wire on my 86 is temp sender going to pass side head. Missing the plastic cover on the clip though.
My AC has green + wire but it’s part of a 2 wire plug and my AC is from an older 70s style AC.
If that helps.