[John in OkieLand]

With this wire removed, the truck starts and runs just fine.
So, what does it supply power to?
It is the one lifted up just above the Positive Terminal


Passenger Side, small gauge

 

[Oneof6]

With this wire removed, the truck starts and runs just fine.
So, what does it supply power to?
It is the one lifted up just above the Positive Terminal


Passenger Side, small gauge


View attachment 187932

Is it charging when it starts? That looks like the wire that powers alternator/generator functions when KOn

 

[John in OkieLand]

no, it is not big enough for the Alternator, it disappears down into the harness below the engine.

here is the Charging wire from the alternator,
that is a 320A MechMan unit.

 

[Oneof6]

Here ya go, see what you think. I know it's not the charging wire. Look at the schematic. I will look at mine in the morning, but I know it's hooked up. No way would I drive with a loose wire lug flopping about close to a battery post. Didn't you have a series of alternator issues? Likely that loose wire is an artifact of that process or a loose end from a mod.

 

[John in OkieLand]

I have the same diagram, and that wire is not Explicitly Shown in it.

I only Lifted it up for the Picture, not driving it with it off.

Just started the engine to see if it was 'necessary'

I suspicion that wire is on another page under "rear axle wiring"

 

[Oneof6]

I have the same diagram, and that wire is not Explicitly Shown in it.

I only Lifted it up for the Picture, not driving it with it off.

Just started the engine to see if it was 'necessary'

I suspicion that wire is on another page under "rear axle wiring"

It's a charging system schematic, it only shows that system, the other heavier cables in your photo are for battery cross over and starter direct power. The wire size on the schematic and fuse links match the schematic.

 

[John in OkieLand]

if you are referring to the wire that goes to Pin 3 on the Alternator, that is not used for my MechMan alternator.

it only has two wires to it, 'I' ( from F-45 ) and "sense" which the Alternator provides either 3-6 volts Key OFF, or 12-15 volts engine running back to the truck wiring.

Actually, on the Mechman, the "sense" only provides 38mV key off.

 

[klhansen]

The only small diameter wire shown on the wiring diagrams coming off the batteries is one going to a junction block then thru a couple fusible links. If disconnected, there'd be no power to the central junction box and the truck shouldn't run. The diagram doesn't specify which battery it comes off of.

 

[Oneof6]

The only small diameter wire shown on the wiring diagrams coming off the batteries is one going to a junction block then thru a couple fusible links. If disconnected, there'd be no power to the central junction box and the truck shouldn't run. The diagram doesn't specify which battery it comes off of.

Exactly, so if those wires are disconnected, and it actually does run as John noted, then a mod must have been made somewhere that turned that depicted connection into an artifact.

 

[bugman]

I have seen where a fuseable link is blown and it has been replaced by a solid piece of wire.

To figure out just where it goes or does you are going to have to trace it out even if it disappears into a wire loom

 

[John in OkieLand]

ya'll came up with the same conclusion that I did.

I have not located the Fusible Links yet, meaning I have not opened any wire looms.

My biggest concern is the 'I' wire is not working, but the fuses are good.

I have not tried to trace from the fuse box thru the harness,
IMO, that is not worth the effort, I think that I will just find the bottom of fuse F-35 and run a new wire to the Alternator "I" terminal and be done with it.

I do not need the light bulb to tell me that alternator is good or bad, I have the digital VM in the power port for that.

 

[Oneof6]

ya'll came up with the same conclusion that I did.

I have not located the Fusible Links yet, meaning I have not opened any wire looms.

My biggest concern is the 'I' wire is not working, but the fuses are good.

I have not tried to trace from the fuse box thru the harness,
IMO, that is not worth the effort, I think that I will just find the bottom of fuse F-35 and run a new wire to the Alternator "I" terminal and be done with it.

I do not need the light bulb to tell me that alternator is good or bad, I have the digital VM in the power port for that.


View attachment 187935

John, in the attached photos of my 02 F250 one can see where I rerouted and upgraded the PS alternator powercable, added a 150A fuse and moved the cable you asked about from the battery post to the side of the new fuse. There is a photo pointing to it leading from the new fuse block. It's a two cable wrap, the larger of the two in that wrap, maybe a #8 goes to the starter solinoid and the smaller line fused wire is the alternators constant 12V " exciter " source. Essentially, my systems circuits are stock design, just heavier cables and a more convenient + side fuse block. Plus a direct alternator case to ground cable.

 

[John in OkieLand]

John, in the attached photos of my 02 F250 one can see where I rerouted and upgraded the PS alternator powercable, added a 150A fuse and moved the cable you asked about from the battery post to the side of the new fuse. There is a photo pointing to it leading from the new fuse block. It's a two cable wrap, the larger of the two in that wrap, maybe a #8 goes to the starter solinoid and the smaller line fused wire is the alternators constant 12V " exciter " source. Essentially, my systems circuits are stock design, just heavier cables and a more convenient + side fuse block. Plus a direct alternator case to ground cable.

I bought a 300 amp fuse and block for the purpose, just need to get it installed now.

Fuse Block

300A FUSE

I also have this Hydraulic Crimper to make sure the Terminals are tight.


Hydraulic Crimper

 

[Maryland dieselnick]

Is your air intake heater hooked up? That looks like it’s relay lead. Post some better pictures of the engine.

 

[Maryland dieselnick]

Here you go John. It’s fir your air intake heater relay. You definitely want to see what is going on there so you don’t have a short and fire.

 

[John in OkieLand]

Thanks guys,
the truck is at a shop now waiting for the TrueTrac install on Monday.
I am to pick it up Tuesday,

Will get better Pictures then for better Clarification.

From another thread, for those who may wonder?
The Alternator Ignition Wire issue has been Resolved, I can now use the key to wait for the WTS light, and start the engine, and the Glow Plugs are not in danger anymore.