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One of Ford's traditional Yellow w/black wires is for the Left Turn Signal/Brake lamp circuit. Any chance you can trace it up to the steering column at one end, or if that's the end hanging, test it back to the left side tail light?
Or for less trouble maybe, if there is a connector under the hood for the rear harness, maybe you can separate the connector and test the ends.
Sorry my diagrams are for newer trucks, but many of the colors are consistent. Fordification has great resources of wiring diagrams. Usually someone has a link or will post up a copy.
thank you @1TonBasecamp i found that resource on fordification and thought it was the left turn signal too but on one of the charts i found (see attached) shows that the yellow turn signal wire doesnt have a black stripe, the orange wire thats there goes to the wiper motor switch, im hoping its a hot wire that i can use for the radio but im pretty far from being able to put in a battery and checking, just putting cab back together and wanted to put in the dash cluster (f600)
Interestingly enough, many of the colors fade or more literally transform to other colors over time. Would not surprise me at all to find that the current black stripe used to be a blue stripe. But what would surprise me would be if that wire was for the tractor trailer circuit breaker!
As your chart shows and as my later experiences tell me, the solid Yellow wires were all full time 12v to power something or another. All the ignitinon switch power wires I've ever seen were solid Yellow. Same for the horn relays and the alternator regulator "A" wires. As well as the ammeter shunt wires. Only later (I believe) did Ford add a white stripe to the Yellow wires on the "A" terminal of the regulator. Not sure why they changed that one and not some of the others.
This is for the '71 in your signature? If it was a '72 I'd just have said that this was a running change made to the colors getting ready for the '73 changes. Ford did that quite often.
One of the major misses that the aftermarket shop manuals had in their diagrams, possibly due to Ford either not giving them the current info, or Ford perhaps not listing the running change made to the Early Broncos was that the '71 wiring diagrams showed the same as the '70 and earlier models. When in fact the '71 model year changed the entire wiring harness orientation! The wire colors remained the same, but the way it was wired and the routing that the wires took to get to their specific duties was nothing at all like the '70 model. Yet none of the diagrams reflected this. And then in '72 (and maybe this had something to do with the inconsistencies?) Ford changed entirely the way they drew wiring diagrams. From the simple "picture" so to speak of the wire routing and function, to some kind of space age mish-mash of strange and mysterious lines across the page. Then in '73 they changed to what looked more like a modern diagram for the next 10 years or more. Then they changed again when things started getting really fancy and including lots of electronics in the early to mid '80's.
So maybe there are some changes in your truck that are just not documented.
One way to find out though!
When you get that battery connected let us know what you find. Whether it's always hot, switched hot, or something else.
In the meantime, any way to see where it goes now?
thanks Paul, yes its for my 71 and you enlightened me as the listing on fordification misses my year mostly so i am stuck with trying to piece it together myself and i am no edison, i will keep you posted on this and certainly be calling on your knowledge
