1 wire alternator set up

[Chester allen]

What is this wire for?

View attachment 955738

Have you disconnected this connector, and checked the contacts?
What color are the wires on the far side, that the BK/YL wires (both) connect to?

View attachment 955739

the one red wire in the first photo goes to my switch panel for offroad lights.

and for the connecter whet do you mean on the far side closer to the batter or firewall?

 

[Chester allen]

If the other wire at the relay is yellow with a fusible link, that’s normal and it is for the horn relay.
Horn relay is usually mounted to the fender apron nearby.

it is yellow but unsure if its a fusible link has tape wrapped over it but was never a issue

 

[mdainsd]

O/P, where are you in California? If close I can help, if you need it. Im not sure why the Ammeter function was disabled in that hook up diagram, but that is another subject.

 

[Chester allen]

O/P, where are you in California? If close I can help, if you need it. Im not sure why the Ammeter function was disabled in that hook up diagram, but that is another subject.

I'm located in west Covina ca @mdainsd

 

[Oldtimer]

and for the connecter whet do you mean on the far side closer to the batter or firewall?

Closer to the firewall.
Ford does not always have the wires on both connectors the same color.
BK/YL in is not always BK/YL out.

 

[mdainsd]

I'm located in west Covina ca @mdainsd

Its a drive as Im in San Diego, but if you end up needing the help, let me know. When I was a kid I grew up in WC.

 

[Chester allen]

Closer to the firewall.
Ford does not always have the wires on both connectors the same color.
BK/YL in is not always BK/YL out.

let me check and ill get back with you.

 

[Chester allen]

Its a drive as Im in San Diego, but if you end up needing the help, let me know. When I was a kid I grew up in WC.

oh yeah Ur a little bit of a drive I'm hoping i can get it going before KOH

 

[Chester allen]

Closer to the firewall.
Ford does not always have the wires on both connectors the same color.
BK/YL in is not always BK/YL out.

one wire is black and one is black and yellow going into the firewall

 

[Oldtimer]

The connector in your first photo looks like C-206 in below schematic.

It should of had a BK/YL, RD/GN, and BK/RD wire, but the factory used what they had on hand when they built the harness.

The cut BK/YL wire in this photo should have been BK/RD with a splice to the fusible link that connected to B+ side of relay.

If the BK/YL wire that is NOT cut is connected to battery +, then the cut BK/YL battery should have 12v.

Here is a link to a 75 schematic: thanks to Steve83
Sheet 1 https://www.supermotors.net/registry/media/879816_1
Sheet 2 https://www.supermotors.net/registry/media/874225_1
Sheet 3 https://www.supermotors.net/registry/media/874226_1

 

[DirtDonk]

If the BK/YL wire that is NOT cut is connected to battery +, then the cut BK/YL battery should have 12v.

That’s a great point Oldtimer. No need to extend it and connect it to the battery just yet. Just look for 12 V on the end of that wire and see what you find.
Measure with a meter that’s cut good resolution. That way you can detect any voltage drops present in that length of wire.

The problem, as always, is that a volt meter might register 12 V, but there’s not enough current capacity to power of any accessories.
For that you might need other tests. Including connecting it to the battery.
But initially, just measuring voltage should be a good start.

 

[Chester allen]

The connector in your first photo looks like C-206 in below schematic.

It should of had a BK/YL, RD/GN, and BK/RD wire, but the factory used what they had on hand when they built the harness.

View attachment 955740

The cut BK/YL wire in this photo should have been BK/RD with a splice to the fusible link that connected to B+ side of relay.

View attachment 955741

If the BK/YL wire that is NOT cut is connected to battery +, then the cut BK/YL battery should have 12v.

Here is a link to a 75 schematic: thanks to Steve83
Sheet 1 https://www.supermotors.net/registry/media/879816_1
Sheet 2 https://www.supermotors.net/registry/media/874225_1
Sheet 3 https://www.supermotors.net/registry/media/874226_1

yes i put my meter to the cut one and it has 12v with key off though.

 

[Chester allen]

That’s a great point Oldtimer. No need to extend it and connect it to the battery just yet. Just look for 12 V on the end of that wire and see what you find.
Measure with a meter that’s cut good resolution. That way you can detect any voltage drops present in that length of wire.

The problem, as always, is that a volt meter might register 12 V, but there’s not enough current capacity to power of any accessories.
For that you might need other tests. Including connecting it to the battery.
But initially, just measuring voltage should be a good start.

its pulling 12v almost 13 with they key off.

 

[Oldtimer]

yes i put my meter to the cut one and it has 12v with key off though.

Key should be off.
This means power is going from battery, thru firewall, across dash to ammeter, back across dash, and back out thru firewall.

Now you get to root around behind dash, and trace the wire.
Somewhere buried in the harness is a splice (maybe more than one) in BK/YL wire that connects the YL (yellow) wire that leads to ignition switch, and the BK/OR wire that leads to fuse block.

I thing the fues block in 75 was in the glove box?
Do any of the fuses have power with key OFF? If yes, BK/OR wire should be good. If no, follow BK/OR wire to splice at BK/YL wire.

Does the YL wire feeding the ignition switch have power? If yes. YL wire is good to here. If no, follow YL wire to splice at BK/YL wire.

its pulling 12v almost 13 with they key off.

As DirtDonk points out, the connections in the harness may be good enough to provide 12v, but not robust enough to supply a load.
Can you attach a jumper to the cut BK/YL wire and connect it directly to a headlight bulb, and then measure the voltage of cut BK/YL wire?

 

[Chester allen]

let me check i will get back to you in 10.

 

[Chester allen]

Key should be off.
This means power is going from battery, thru firewall, across dash to ammeter, back across dash, and back out thru firewall.

Now you get to root around behind dash, and trace the wire.
Somewhere buried in the harness is a splice (maybe more than one) in BK/YL wire that connects the YL (yellow) wire that leads to ignition switch, and the BK/OR wire that leads to fuse block.

I thing the fues block in 75 was in the glove box?
Do any of the fuses have power with key OFF? If yes, BK/OR wire should be good. If no, follow BK/OR wire to splice at BK/YL wire.

Does the YL wire feeding the ignition switch have power? If yes. YL wire is good to here. If no, follow YL wire to splice at BK/YL wire.

View attachment 955771


As DirtDonk points out, the connections in the harness may be good enough to provide 12v, but not robust enough to supply a load.
Can you attach a jumper to the cut BK/YL wire and connect it directly to a headlight bulb, and then measure the voltage of cut BK/YL wire?

So yes the yellow wire gets 12v i took my ignition apart to check that and it is indeed pulling 12v but that post on the back still is getting 12v this is key off the ignition is out of my dash

 

[Chester allen]

Key should be off.
This means power is going from battery, thru firewall, across dash to ammeter, back across dash, and back out thru firewall.

Now you get to root around behind dash, and trace the wire.
Somewhere buried in the harness is a splice (maybe more than one) in BK/YL wire that connects the YL (yellow) wire that leads to ignition switch, and the BK/OR wire that leads to fuse block.

I thing the fues block in 75 was in the glove box?
Do any of the fuses have power with key OFF? If yes, BK/OR wire should be good. If no, follow BK/OR wire to splice at BK/YL wire.

Does the YL wire feeding the ignition switch have power? If yes. YL wire is good to here. If no, follow YL wire to splice at BK/YL wire.

View attachment 955771


As DirtDonk points out, the connections in the harness may be good enough to provide 12v, but not robust enough to supply a load.
Can you attach a jumper to the cut BK/YL wire and connect it directly to a headlight bulb, and then measure the voltage of cut BK/YL wire?

And for the bk/yl cut wire can i use any gauge wire? And how would i go about connecting it to my lights?

 

[DirtDonk]

Just as a reminder, the reason that the one wire has the 12 V reading on it, even without the key on, is because it’s the same wire.
If you trace the one black with yellow wire, that’s still intact and connected to the starter relay, all the way through the harness it comes back out and is that same way that you cut.
Other than a couple of splices a junctions in various places, it’s essentially one wire.
So you’re measuring voltage on the far end of that same wire. Looped around.
There’s no switch or fuse in between.

 

[DirtDonk]

So yes the yellow wire gets 12v i took my ignition apart to check that and it is indeed pulling 12v but that post on the back still is getting 12v this is key off the ignition is out of my dash

Then your switch, or something inside the connection, is fubarred.

 

[Chester allen]

Just as a reminder, the reason that the one wire has the 12 V reading on it, even without the key on, is because it’s the same wire.
If you trace the one black with yellow wire, that’s still intact and connected to the starter relay, all the way through the harness it comes back out and is that same way that you cut.
Other than a couple of splices a junctions in various places, it’s essentially one wire.
So you’re measuring voltage on the far end of that same wire. Looped around.
There’s no switch or fuse in between.

so theoretically i connect the other wire to + side of starter relay i should get power back again like i had before swapping it no? because it was fine before but my confusion is about the junctions/splices in between could my new amp be to powerful for those junctions? did i go up to many amps that my wiring cant support it? and now I'm wondering if my stock alternator was fine it was just the wiring behind the dash that is messed up not being able to recharge my battery? because the reason i did this is because i was able to start my bronco a few times with a fully charged battery but after a few start ups my battery was already dead. witch is why you see some wires melted because i would try to crank it over and sometimes after a few cranks that wire was how and melted I'm guessing i just never saw because hood was closed.