I’m going through all the wires that pass through the firewall of my 1976 F150. I bought the Dakota Digital gauges and an HEI, so I was able to delete a bunch of the old wiring harness. Of all the wires I have left, there are 3 that I can’t identify:



All three are coming through the passenger side firewall. One is green with black stripe and has uninsulated quick disconnect type terminal, one is black and yellow (it’s fat, but not as fat as the black/yellow wire that comes off the starter relay), and one is white with black stripe and ends with a connector that looks like a stereo/headphone jack.

Can anyone tell me what these wires are used for?

 

Just gonna bump this up and hope that one of the wiring gurus will see it.

@1TonBasecamp maybe?

 

I think black/yellow should be your heater blower motor. White/black is probably the wire from the alternator stator for the electric choke...The green wire probably had a plastic connector on it originally...dont' recall what it's for...I'll check out the schematic...the only green/black I see is for the high-beam headlight circuit (including high-beam indicator in the instrument cluster)...

 

Thanks. I followed the wires and it does appear that the black/yellow wire goes to the heat/air system. The green wire actually looks green/yellow inside the dash and that one went behind the passenger side air vent. I’m guessing it must have something to do with the radio. The white/black wire goes into a connector:


then the baby blue wire coming out of that connector goes through the firewall and eventually goes into the fuse block. Any idea what that is?

Btw, I’m planning to get an after market A/C system. Probably Vintage Air. Any idea if I’ll need any of the wiring that went to the old heat/air components? I’ll look through the installation manual, but I’m hoping I can delete a bunch of the old harness.

 

Is the wire near the passenger vent terminated by a single bullet connector (what's the technical term?). I think that might have gone to a plunger switch for the courtesy light on the passenger door jamb.

 

the blue wire provides power to the throttle emission control solenoid on the carb...

 

You are right. Today I pulled all the heat/AC stuff out of the dash and with that removed I was able to follow the green/yellow wire all the way to the courtesy light switch in the passenger door jamb.

 

Thanks for the shout-out i6. Appreciate the vote of confidence!
Looks like you're fully covered. And I'm always digging into the diagrams because Ford has a way of re-using colors sometimes that is very maddening.
Good description of the Black w/yellow wire being slightly smaller than the one on the starter relay. That's usually my first "assumption" when the subject of Black w/yellow wires under the hood comes up.

Glad you got it sorted. Hopefully it's smooth sailing with cleaning up the wiring mess that's usually under our hoods.

Paul

 

Back when I got the truck and I was driving it every day, I don’t remember if this wire was hooked up to anything. I don’t think it was because I don’t remember a wire hooked up to the carb. Is that possible? Would the 2150 carb have functioned without this?

I’ve deleted parts of the wiring harness several times and I think I’m getting down to the bare bones now. First I put in a 3g alternator which eliminated a bunch of wires. Then I put in an HEI. Then I got new gauges with new sensors and so eliminated the wiring to the old sensors. Then I took out the the old heat/air system along with all those wires in anticipation of getting the Vintage Air SureFit system that just came out for my truck. It’s possible that in one those wire deletion steps, I may have unhooked the throttle emission control solenoid and don’t remember. But if that were the case I would guess it was when I did the 3g alternator swap because I had no clue what most of the wires were for so it’s hard to remember what I did.

I’m also confused by that one because it’s two wires and there’s the connector that both the blue wire and the white wire come out of and then there’s another connector at the end of the white wire. It looks like both of those connections would have been made in the engine bay.

 

It's not connected directly to the carb, but to a dashpot looking thingy sitting in front of the throttle linkage on the side of the carb. But you'd still have seen a wire connected there if it was present.
Most get tossed for lack of understanding, or from failing and the owner simply not wanting to deal with replacing it.

Absolutely. No aftermarket carb comes with one, and they work fine. Most older vintage carburetors from the mid-sixties to the early eighties however, usually came with one type or another from the factory. The carb would still work with this dsabled and the engine would still run, but would be missing some desirable functions nevertheless.

The White w/black wire is the stator wire from the alternator. On a truck with an ammeter gauge originally, and not just a low battery warning lamp, the stator wire has only one single function. It runs between the STA post on the back of the alternator, up to the carburetor's choke housing connector. And that's all ti does.
Since you no longer have a stator output wire that you can utilize for this, hopefully you don't need the factory electric choke anymore. Or if still the original carburetor, you can try to use another wire that's only hot when the key is in the ON position.
The reason for using the stator wire is that it's only hot when the engine is running. So there's no chance that you will turn the key on, wait a few minutes while you're doing something else, and have the choke open up all on it's own because the key is on. Making it potentially hard to start on a cold day.
Some that live at high altitudes however would like that feature. That way they can have the choke open up at least partially before they attempt to start the engine and flood it for being too rich.
But for most people, a working choke is a good thing.

I'm not sure what went where with the connectors, but that's what at least that one wire does.

Paul