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I have an under hood wiring harness from a 65 Series 1 slant 6. In the same bundle that the coil leads are in, there is a red lead that is not marked. Is this the lead to the distributor?
Thanks for clarifying.

- EM

The distributor is only connected to the neg terminal of the coil. That wire is direct between the two and is not in the harness. A red wire goes to the pos terminal of the coil and that is the only harness wire that has anything to do with the coil.

Understood but I already have leads that are marked for Coil Neg and Pos (Sorry but I don't have the lead color with me currently). With that in mind, what is the red lead that comes out of the same bundle?

- EM

Oil pressure sender, water temp sender, alternator + and field.

I already have water temp and alternator battery and field leads isolated so that leaves oil pressure but isn't that a pressure tube (and not a wire lead) to the sending unit at the back of the block?

- EM

If its a sending unit, its an electronic gauge and needs a wire.
A tube is for a mechanical gauge and just connects directly to the block - no sending unit.

is it possible the truck you pulled the harness from had a tachometer ? that wire is usually from the coil..

or maybe it was upgraded from points to pertronix ?? that setup would add an extra red wire to the distributor

Did you compare it to the factory manual diagram?

wally426ci wrote:Did you compare it to the factory manual diagram?

I'm going there next Wally as apparently I haven't been clear in this post.

- EM

I reviewed my shop manual and a couple of other wiring schematics ON-LINE and strangely, the only "Yellow" colored leads I see in these are for various lighting circuits. The yellow lead I'm trying to decipher is definitely an OEM lead and comes out of the original firewall bundle into the engine bay (I bought my truck from the original owner and it is 100% original and untouched). I tried to do some looking on the cab side but could not see where that lead goes.

It would be great if the owner/s of a 64-65 D100 with slant 6 could quickly check under their hood to verify the yellow wire exiting the firewall into the engine bay and where it goes. I should mention that I do not see an oil temp lead (supposed to be white). I do wonder if this "yellow" lead could be for the oil temp but the color doesn't look like a white that has yellowed with time. It looks like a very uniform yellow that was always yellow.

Thanks for your help guys.

- EM

Pull your instrument cluster(easy to do) and see if it is the wire attached to the oil gauge. If you have an oil pressure sender unit, u MUST have a wire for it!

I also vote for oil pressure sender that started out as white and has yellowed.

I have the same as yours, except late 65. I have removed my harness for a rewiring project. Here is photo of the white/yellow wire exiting the harness:
https://www.dropbox.com/s/gxgpiqdgaj2gk ... 4.jpg?dl=0.

I think all of the greasy dirt on the connector confirms it went to the oil pressure sender.
If you keep going down this part of the harness, you get to the wires going to the coil, alternator and water temp sending unit.

there is a yellow wire w/ black tracer for A.C. trucks for the compressor clutch that routes with coil, temp sender, alternator etc.