Victory and defeat… electrical.

[Geep]

Will try to keep this concise… had a great win today, rejetting the weber to c.d. iesel specs and tuning the weber to purr like a kitten… awesome! Leaving the drive on another test drive, the lights flicker and she shuts down. A win with the carb, but a short was in the shadows and it showed itself all of a sudden. So this short resides between the battery and alternator and has affected the wiring group it appears to be routed with. Pictures may not be helpful but they are here. I’ll take all suggestions including those superfluous to my issue but addressing electrical cuz that’s definitely the problem. At the moment the vehicle is a brick, no fuses blown (so a short within the circuit). The heat has damaged other wire groups and the battery as you might can tell from the pictures. I’ll chase any rabbits… any observations or input welcome. 
I realize imagine may lack detail, I’m happy to follow up on assignments to track things down. Just a tough electrical loss after a great fuel system win 😞

[2002iii]

I would replace that wire with a bigger one.

[Mike Self]

Keep in mind that the wiring to and from the alternator and voltage regulator is not fused.  And that includes the heavy gauge wire that's fastened to the + battery terminal.  In fact, any solid color wire (original, not messed with by a PO) in the harness is not fused (brown wires are ground wires), so you can have a dead short, melted wires etc without a blown fuse.  And somewhere in that wiring set, there was a bare wire that grounded, causing all this mess.

 

mike

[OldRoller]

In the last picture there are two wires going to the alternator B+ terminal. What does that heavily burned wire supply? 

there should never be more than the single alt to battery wire on that terminal.

[John76]

As @Mike Self pointed out, the solid Red wires are always HOT (+12V) and NOT fused.

I refer to these as the "Fire Wires" or the "Fryer Wires"...your choice.

Follow the Red wires on the attached schematic to make sure nothing is shorted to ground.

The Black/red wire from the starter (tab #15) to the coil (+) is HOT only during starter cranking but is not fuse protected. If this is shorted, you get crispy wires when you start your car!

Any other wire connected to the alternator B+ should be fuse protected. This is sometimes used as a convenient power source for aux. relays, etc....

3 hours ago, OldRoller said:

What does that heavily burned wire supply? 

Obviously not protected by a correct fuse and/or the wire size to handle the load! 

 

John

 

 

[Geep]

This is gold. Thank y’all… they all have their quirks, been working on scouts for a couple of years and if anyone ever refers to a ‘green wire’ its useless. They are almost all green haha. 
 

thanks for pointing me in the right direction. 

[Mike Self]

EDITED

 

Several more "needs to know"--3 through 5 are new:

 

1.  Make sure the ground strap from the - battery terminal to the body is tight and clean at both ends.  Lacking that strap, when you pull 200 or so amps while the starter is operating, the only ground path back to the battery is via the accelerator linkage--which wasn't designed for that!

 

2.  Make sure the brown ground wire running from the alternator frame to the engine block is present, and that it hasn't frayed down to a couple of strands under the ring terminal ends (they do that)  That's the only good ground path for the alternator's - current to flow due to its rubber mounts.

 

3.  It appears that the battery in your car is not even close to correct--the terminals are reversed from were the factory wants 'em:  positive should be at the car's front; negative at back, and those side terminals are just begging to short out on something metal and really cause fireworks.  You need a Group 26R battery with top terminals, and the positive one at the car's front.

 

4.  From the pictures you just posted, I can't see either a ground strap on the negative terminal, or a proper positive cable on the + terminal--just a heavy gauge (10 perhaps?), where it should be 2 or 4 gauge.  Anything smaller will overload from the starter motor's draw.  

 

5.  I'm sure John76 has a ready-made drawing of those unfused wires that link alternator, battery, voltage regulator and starter; you may be better just to get some heavy gauge (err on the side of caution and use 10 gauge) wire in colors that match the original wiring and make a whole new harness for that part of the wiring.  What you have is good for copper recycling and not much else.

 

mike

Edited February 2 by Mike Self
Additional information

[John76]

16 minutes ago, Mike Self said:

Make sure the brown ground wire running from the alternator frame to the engine block is present,

Good practice is to make the ground wire the same gauge as the wire to the B+.

Especially if you upgrade from a 45A alternator to a 100A.

 

 

[Geep]

5 hours ago, OldRoller said:

In the last picture there are two wires going to the alternator B+ terminal. What does that heavily burned wire supply? 

there should never be more than the single alt to battery wire on that terminal.

As far as I can tell it appears extra and runs parallel to the main larger gauge wire. The only thing I see (which doesn’t tell me much) is that it is crimped in a ring connector with the same wire that runs to a large relay that lives under the ignition coil. I have not learned what that is yet…

[Geep]

1 hour ago, John76 said:

Good practice is to make the ground wire the same gauge as the wire to the B+.

Especially if you upgrade from a 45A alternator to a 100A.

 

 

Its just a piece of green 12ga thhn… oy, I have some digging to do for sure. She’s all hacked up. Guess it’s how I’ll learn it. 

[AceAndrew]

2 hours ago, Mike Self said:

 

 

2.  Make sure the brown ground wire running from the alternator frame to the engine block is present, and that it hasn't frayed down to a couple of strands under the ring terminal ends (they do that)  That's the only good ground path for the alternator's - current to flow due to its rubber mounts.

 

mike

 

I'll emphasize this.  Had the same happen to my car and it tried to ground through that line going to the regulator.  

 

 My alternator-engine ground wire was present, but when I checked the resistance .... it was through the moon.  Brittle, old, and too small to begin with.

[Rich]

This was GREAT info, John has helped me out before with electrical gremlins and his charts and diagrahams are the best, good luck, 

[Geep]

3 hours ago, John76 said:

As @Mike Self pointed out, the solid Red wires are always HOT (+12V) and NOT fused.

I refer to these as the "Fire Wires" or the "Fryer Wires"...your choice.

Follow the Red wires on the attached schematic to make sure nothing is shorted to ground.

The Black/red wire from the starter (tab #15) to the coil (+) is HOT only during starter cranking but is not fuse protected. If this is shorted, you get crispy wires when you start your car!

Any other wire connected to the alternator B+ should be fuse protected. This is sometimes used as a convenient power source for aux. relays, etc....

Obviously not protected by a correct fuse and/or the wire size to handle the load! 

 

John

 

 

This schematic is great… but it doesn’t match what I have in my floyd workshop manual. It DOES however (from what little I can see) appear to better match whats actually in my 1976 ‘02 4speed. Im trying to work through where all these things go, what various disconnected plugs are etc. Can you share a schematic, or recommend a better service manual than what I’m working with?

[John76]

1 hour ago, Geep said:

the same wire that runs to a large relay that lives under the ignition coil.

Can you snap a picture of this?

May be an external resistor relay if the original resistor wire was removed.

 

[John76]

12 minutes ago, Geep said:

Im trying to work through where all these things go, what various disconnected plugs are etc.

A picture would help. Clean off the wires and describe the color codes of what is disconnected.

Is your '76 a 49-state or CA spec car? There are subtle differences between the two.

Thanks,

John