Fusible link/ignition wire troubleshooting

[Ihavea73]

Needed to jumpstart yesterday and apparently burnt up a wire (s). With battery or charger hooked up, nothing happens with key on accessory or ignition.

Have removed the battery and plan on replacing it for the season. After researching on here, thought that it was the fusible link wire. It looks like the tag was melted in the past as it looks dirty to me and not fresh.

Started pulling some of the electrical tape off and the brown wire has melted insulation.

I am an amateur and do not know where the other end of either of these wires are and would prefer not to continue removing tape and tracing all of this back and end up in deep over my head. Can I snip off the brown wire where the wire still appears good and splice in new? How do I know if the fusible link wire is good or bad?

Thanks in advance

 

[Oldtimer]

What year Bronco, and stock harness?

 

[Ihavea73]

Also, it appears the insulation melted off the brown wire previously as well, because it seems to be dirty and does not look fresh.

<a data-flickr-embed="true" href=" https://flic.kr/p/2qXyQB7 " title="IMG_8642"><img src="https://live.staticflickr.com/65535/54450069348_1b95b3acaf_k.jpg" width="2048" height="1536" alt="IMG_8642"/></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

 

[DirtDonk]

More pictures, please. A little broader scope as well
Is that an ignition coil mounted to the inner wheel well?
The brown wires only function is to connect to the ignition coil during START. It failing by itself, would have nothing to do with not having power anywhere else. The only things that can do that are the fusible link on the black wire, and the main battery cables themselves.
That does not look like a factory fusible link to me either, so it may have been replaced at some point in the past.
The wire on the link is gray, but you should remove some more of the tape to see what color the wire is that it connects to. Gray is not a normal color in that area at least that I can remember.

 

[DirtDonk]

In fact, looks like a lot of non-factory wires under there. Maybe just for an aftermarket ignition?
What else?

 

[Ihavea73]

https://flic.kr/p/2qXtPiz https://flic.kr/p/2qXyeB5 https://flic.kr/p/2qXyeBa

 

[Ihavea73]

I can reorganize this birds nest and get another picture later this week if it will be helpful.

 

[Ihavea73]

https://flic.kr/p/2qXzyqH

 

[EPB72]

https://seabiscuit68.tripod.com/. link to wiring diagrams. but you have some added and/or non oe stuff ,,,, was the fuse link label just a casualty of the ignition bypass melt down?? so at the fuse link the yellow wire would go to the fender mount voltage regulator if thats still being used I would check for power there ,,, the black red wire coming out of fuse link goes to amp meter loop and splices in power to ignition and to the black yellow wire coming out of the harness next to fuse link in your picture that should go to the alternator charge wire , check for power ther and at the voltage regulator , if you have power at one or both the fuse link is most likly ok ish , if so you probably will be looking for issues under the dash.. .

 

[DirtDonk]

You got a lot going on under that hood!
Yes, a rats nest now. But perhaps not so bad once you get things figured out.
And I guess I was wrong on that not being a factory fusible link. But that was also why I was asking what year your bronco is. That’s obviously a factory splice that was under all that tape.
Kind of wondered about that, because the bulge in the tape didn’t look like a typical crimp connector size. More like the big blob of a factory splice.
How many amps output is your alternator rated at?
And is that battery disconnect switch, simply an on off safety thing or is it a dual battery switch?

Thanks for the pics. Even though it didn’t result in an immediate answer of what’s what, they are a huge help.

 

[Ihavea73]

There is a battery disconnect switch, all of this was here when I purchased it.

It's a 1973

 

[Oldtimer]

Nothing happens when ignition switch turned to RUN or ACC.

Stock harness power flow is from battery (BK wire fusible link) thru bullet connector at ammeter,
then to a splice under dash that feeds
1) ignition switch (Y wire),
2) headlight switch (BK-O wire) and
3) back to alternator (BK-Y wire).

If bullet connector is unplugged or corroded, there will be no power to switches.

These two wires (BK fusible link and BK-Y alternator plug) should have continuty end to end if stock harness is not compromised.

I think you have a 73 Bronco.
The wire colors conform to 72 harness per seabiscut68 schematics.

 

[Ihavea73]

At the bottom picture with the three wires going into a plug - none of that is in use. That plug is not plugged into anything and those wires are cut out where they all enter the cab.

 

[Oldtimer]

When fusible link is connected to battery, at starter relay, do the headlights work?

 

[Ihavea73]

Update:

The motorcraft battery that was in it (18 months old) was shot. It had 3 bad cells. Battery has a 36 month warranty and local dealer would not do a warranty exchange saying they needed it to be in the vehicle for the exchange. Went to Interstate and got a new battery.

The connection between fuseable link wire and starter solenoid (or relay - I don't know the correct term) seemed very week so I cut it off and replaced it with a crimp on connector I had in my toolbox. Here is a picture of the old connector.

Reconnected everything and it fired up better than it ever has in the two years I have owned it.

Question: is the burnt up brown wire not in use?

https://flic.kr/p/2qY1egF

 

[DirtDonk]

The connection between fusible link wire and starter solenoid (or relay - I don't know the correct term).

It’s a relay. That’s what Ford called it from as far back as I’ve seen documentation.
But it can loosely be called a solenoid because of the millions of people that call it that, and because nowadays even package labeling often calls it that. Bowing to public opinion perhaps.
Mag-switch, contactor, probably other names with various meanings and different functions sometimes. But a “relay” is a magnetically controlled switch. A “solenoid” must do physical labor. Such as pushing a gear into contact with another gear.
Possibly a Ford starter relay might be referred to as a solenoid, because it closes a heavy duty electrical contact. But to me, that still makes it a relay/switch.

Question: is the burnt up brown wire not in use?

Depends upon your type of ignition. But from the looks of it, you probably don’t need it right away.
It’s still serves a double duty as a back up in case the ignition switch starts to fail to the point where the ignition system no longer gets a signal in the START position. I considered a failure, but it’s a very common mode for our Old Ford ignition switches. Turn the key too far, and the ignition drops out. At some point though, it drops out constantly. When that happens, the brown wire is a back up.

 

[Oldtimer]

In a stock harness the other end of the BR wire is spliced to the pink resistance wire and the coil power feed. When key is in RUN position the BR wire at the relay end should have 8ish volts on it, so it should be insulated.
When key is turned to START, the relay supplies 12v to BR wire to provide full voltage back to the coil and increase spark voltage to improve starting.
I suspect with you aftermarket ignition box, the BR wire may not be connected at either end?