White wire partly melted!

[martiq]

Hello

Accidently found this wire in the loom in the fuse/relay compartment.

Unwrapping the loom, I found the white wire partly melted in several places sometime in the past.

It's a relatively thick white wire, and as far as i can see, It's the thickest white wire running to the back of the bulkhead connectors. My guess is it's the one connecting to the yellow bulkhead connector pin 3, meaning it connects to the ballast resistor.

Have any of you seen this before, and does anyone have an explanation to why it happend?

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[Josh]

in my experience that happens due to the wire shorting out somewhere along the line. I would trace it back to the device it is powering, that will help with getting to the bottom of this failure. There are quite a few white wires in the car, it is a switched 12v feed off the aux relay.

Looking over the wiring diagram, circuits powered by the white wire are:

Ignition resistor
Fuse 1
Fuse 3
Fuse 4
Fuse 5

[Nicholas R]

There is a junction in the relay compartment where it appears as though a dozen white wires come together under heat shrink. If I recall correctly they are fed by the negative side of the ignition coil (essentially the tach signal). Can't tell from the photo if that is one of those white wires.

[Josh]

There is a junction in the relay compartment where it appears as though a dozen white wires come together under heat shrink. If I recall correctly they are fed by the negative side of the ignition coil (essentially the tach signal). Can't tell from the photo if that is one of those white wires.

those are white/grey wires

[Nicholas R]

those are white/grey wires

Damn, you're totally right. My bad. I'm surprised I forgot that; I spent so much time isolating those wires individually when I was trying to get my engine to jive with the stock tach.

Anyway, disregard what I said above.

[martiq]

There is a junction in the relay compartment where it appears as though a dozen white wires come together under heat shrink. If I recall correctly they are fed by the negative side of the ignition coil (essentially the tach signal). Can't tell from the photo if that is one of those white wires.

No Nicolas you are right,. There are several junctions in the compartment, and as I already mentioned it's the white wire that runs to the yellow bulkhead connector.
Josh:You are talking about another junction (please see this better picture) but you did correctly mention in your first post, that the white powers the resistor ;-)

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It's exactly one of the thickest wires from a big white junction, and the wire is the supply power to the coil through the yellow bulkhead connector pin 3 and via the ballast resistor. It's powered from ign.pos 2.

My theory is: I'm missing the small supressor a the coil. That might have been faulty at some point in the past and shorted out the circuit, and "boiled" the white wire. The supressor had then been removed.(and in addition to that other components as maybe the ballast resistors etc has been changed.) But nobody payed attention to other damages deep in the wiring-loom....How does that sound as explanation???

Regards

[David T]

No Nicolas you are right,. There are several junctions in the compartment, and as I already mentioned it's the white wire that runs to the yellow bulkhead connector.
Josh:You are talking about another junction (please see this better picture) but you did correctly mention in your first post, that the white powers the resistor ;-)

29028

It's exactly one of the thickest wires from a big white junction, and the wire is the supply power to the coil through the yellow bulkhead connector pin 3 and via the ballast resistor. It's powered from ign.pos 2.

My theory is: I'm missing the small supressor a the coil. That might have been faulty at some point in the past and shorted out the circuit, and "boiled" the white wire. The supressor had then been removed.(and in addition to that other components as maybe the ballast resistors etc has been changed.) But nobody payed attention to other damages deep in the wiring-loom....How does that sound as explanation???

Regards

If that suppressor was bad and shorted to ground it would have made a mess by the coil. Somehow, someway too much current was drawn through that wire at some time in the past. You really should cut out the burnt piece and replace it. I would carefully inspect the entire wiring harness for other damage. When 1 wire burns it damages the insulation on adjoining wires. It also takes all of the spring out of the connectors so they should be replaced too. On one car I worked on, the brown wires were all "french fried" because the owner stuck the wrong relay in the wrong spot. By the time he realized his mistake things were already cooking well!

[martiq]

Yes. I'm replacing the wire for sure, and going to check everything else. So far i just found some small spots with evidence of slightly melted insulation on another wire touching the white wire, This other wire I belive is one of the wires going to (the not used) hot start relay socket.

There are signs of "something happened" around the coil in the past, because the connectors looks to have been replaced and one of the wires is a little short (as if it has been cut).

...And I was only replacing the sound-insuation in the back when i discovered the fault. One task always leads to a new one when restoring a D :yesss:

[martiq]

Update

Today i unwrapped the entire bundle of wires in the compartment (felt like doing surgery)

Some asshole in the past actually did open it, and damaged the insulation slightly on three wires with a knife. The mission obviously was to replace dammaged wires, but he missed the one I found now.

He did find and replaced antother white wire, and re connected it with a rather bad soldering at the (now famous) junction of the white wires. The one replaced is conecting to the blue bulkhead connector pin 27 (it's the one changing to brown in the the engine wiring loom and connecting to the B+ on the early generators. More on that later

It seems logical that this wire also got fried if the suppressor shorted to ground. The rest of the white wires just blew the fuses, and the feed wire from the ignition apparently withstood the heat due to it's larger dimension.

There are no dammage to the loom in the engine compartment. But there are indications that it has actually been replaced, because it's not routed the early way over the top of the intake manifold. My loom is routed at the side and through the intake manifold "legs" and under the W-horn on the intake.

Back to the generator... This leads me to a slight "off topic question" to my problem.

According to service bulletin when changing to Motorola generator, the brown wire is to be cut back at the blue connector (#6 in the bulletin instructions). But then why bother connecting it to the new generator (#14 in the bulletin instruction) I mean: Why connect at wire that has been cut in the other end??? Can someone please spell out the logic in that to me?

The wire isn't in the wiring diagram by the way..

Regards

[martiq]

and here is the service bulletin

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[Bitsyncmaster]

According to service bulletin when changing to Motorola generator, the brown wire is to be cut back at the blue connector (#6 in the bulletin instructions). But then why bother connecting it to the new generator (#14 in the bulletin instruction) I mean: Why connect at wire that has been cut in the other end??? Can someone please spell out the logic in that to me?

The wire isn't in the wiring diagram by the way..

Regards

Maybe so the dangling connector does not short onto something. They should have just cut both ends.

[martiq]

Todays project.

Most of the damage was debris from the burnt white wires. The purple and the orange wire in the pictures suffered some battlescars too.

I cut out everything bad and soldered in new repair wires.

So happy to get the job done that I completely forgot to take a picture of the finished project. Everything is already tugged away behind the backplate.

Guess I will refit the car with a suppressor again, but I will fuse the damn thing thats for sure. Any recommendations om fuse size???

/Martin

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[Bitsyncmaster]

Guess I will refit the car with a suppressor again, but I will fuse the damn thing thats for sure. Any recommendations om fuse size???

/Martin



A capacitor shorting is pretty rare and if they do they usually blow apart. A fuse value would be a pretty complex thing to calculate but I would guess one amp or more would work.

[martiq]

A capacitor shorting is pretty rare and if they do they usually blow apart. A fuse value would be a pretty complex thing to calculate but I would guess one amp or more would work.

Thanks!

Maybe i'm just being paranoid wanting to fuse it. The shortage probably was a damage on the wire part shorting it on the outside metal housing, rather than inside the capacitor itself.

/Martin