What's that thick black wire from the alternator? - Defender Source
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  #1  
Old January 21st, 2014, 01:12 PM
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What's that thick black wire from the alternator?

I have a 200 TDi in a 110. There's a thick (around 8 gauge?) black wire going from the back of my alternator to the frame, right near the front left wheel suspension. The wire is about 10 inches long & is coated.

It eventually wore against an engine mount so bad that it apparently started to arc, causing a bunch of white smoke & the wire has now burned in half.

Is this a ground wire? I thought engine ground straps were bare, like a flat braided copper. And why did it arc? If it was neutral, it shouldn't arc....?

I can't find it on the parts manual

Regards
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  #2  
Old January 21st, 2014, 01:22 PM
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Sounds like a ground wire. On mine is runs from the block to the chassis, not the alternator. There is also one from the starter motor to the block.
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Old January 21st, 2014, 01:28 PM
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Quote:
Originally Posted by Axel View Post
I have a 200 TDi in a 110. There's a thick (around 8 gauge?) black wire going from the back of my alternator to the frame, right near the front left wheel suspension. The wire is about 10 inches long & is coated.

It eventually wore against an engine mount so bad that it apparently started to arc, causing a bunch of white smoke & the wire has now burned in half.

Is this a ground wire? I thought engine ground straps were bare, like a flat braided copper. And why did it arc? If it was neutral, it shouldn't arc....?

I can't find it on the parts manual

Regards
There should only be one black coated earth wire on the front of the starter motor to the engine block, and a flat braided wire from the block to the chassis in that area.

disconnect the battery and remove that wire, from the alternator you should only have two #6 and a #14, don't quote on the sizes.

I can only think a PO fitted a extra earth wire to the alt but is not really needed if all the bolts are righty tighty, why the arcing FK's. maybe a picture or two would be helpful
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  #4  
Old January 21st, 2014, 01:57 PM
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Quote:
Originally Posted by Red90 View Post
Sounds like a ground wire. On mine is runs from the block to the chassis, not the alternator. There is also one from the starter motor to the block.
Is yours from the block to the chassis coated, or bare?

------ Follow up post added January 21st, 2014 12:58 PM ------

Quote:
Originally Posted by roverman2010 View Post
There should only be one black coated earth wire on the front of the starter motor to the engine block, and a flat braided wire from the block to the chassis in that area.

disconnect the battery and remove that wire, from the alternator you should only have two #6 and a #14, don't quote on the sizes.

I can only think a PO fitted a extra earth wire to the alt but is not really needed if all the bolts are righty tighty, why the arcing FK's. maybe a picture or two would be helpful
So no coated wire from the alternator to chassis?

------ Follow up post added January 21st, 2014 12:59 PM ------

Good idea but I can't get a picture - it's in a shop about 30 minutes away. If they still can't figure it out by tomorrow, I will snap a pic.
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  #5  
Old January 21st, 2014, 02:07 PM
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I can't recall if mine are both insulated or not. Could look later. I suspect these things change over the years. Can you take a photo? I think the block connector might be one of the alternator mounting bolts.
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  #6  
Old January 21st, 2014, 04:40 PM
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This may help you

Quote:
Originally Posted by Axel View Post
I have a 200 TDi in a 110. There's a thick (around 8 gauge?) black wire going from the back of my alternator to the frame, right near the front left wheel suspension. The wire is about 10 inches long & is coated.

It eventually wore against an engine mount so bad that it apparently started to arc, causing a bunch of white smoke & the wire has now burned in half.

Is this a ground wire? I thought engine ground straps were bare, like a flat braided copper. And why did it arc? If it was neutral, it shouldn't arc....?

I can't find it on the parts manual

Regards
Axel:
This why test lights were invented.
Since you don't state precisely where it attaches in the back of the alternator and if it is actually bolted to the frame it is hard to tell if it is (+) or (-).
You say it rubbed through the insulation and arched????

A (+) wire hooked to the "back of the alternator" would surely arch if it had insulation worn through and attached to the back of the (+) alternator lead and disappeared somewhere near the frame under the vehicle (to presumably connect something up that draws (+) current).

OR

It could be strictly a PO stupid wiring that is very very commonly executed by people who have no real fundamental understanding of vehicle wiring.
Here are the cliff notes of grounding (-) current as follows.
The vehicle, engine, frame, transmission, and suspension (mostly) is grounded (or should be).

The (-) battery terminal is connected to the frame, the frame has a ground cable to the engine, and this creates (-) ground. Knowing this, there is NO NEED to connect separate ground wires from or to the starter or alternator.

BECAUSE

Anything bolted to the engine will be grounded with (-) current. If the engine is grounded and you bolt something to it that is made of metal that conducts electricity (like steel or aluminum) then it will also be grounded. So running a ground wire to something that is already grounded is a waste of resources. In summary running a ground wire to something that is already grounded is unnecessary for obvious reasons.

EXCEPT

Except for the case where you have a bad ground already and someone who doesn't know how to fix the problem runs a new wire to say ground an alternator that is not charging because of the faulty ground between the engine and frame or between the battery and frame. In this case the real cure is to fix those faulty grounds and NOT run an new ground wire.

I have fixed so many electrical problems by simply removing the ground cables, cleaning away old paint and corrosion and reattaching them. A bad ground can cause all sorts of weird problems as electrical devices that should be grounded search for a ground. This causes things like accelerator cables to glow red and catch fire as an example.

Hope this helps.
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  #7  
Old January 22nd, 2014, 12:42 AM
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Good points, Richard
I called the shop this afternoon to tell them some of the things you guys suggested & they said "Don't worry, we got it." So naturally I'm worried (because a prior shop had exactly said that before attaching that alternator wire!) I'll let you know.

Jack
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  #8  
Old January 22nd, 2014, 07:53 AM
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A shop manual will also have proper wiring schematics for the entire truck- think if you were half way home from a movie after dark, or any time any where. A rudimentary tool kit with test light and said manual are basic kit for every Rover...
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  #9  
Old January 22nd, 2014, 08:06 AM
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Quote:
Originally Posted by Axel View Post
Good points, Robert
I called the shop this afternoon to tell them some of the things you guys suggested & they said "Don't worry, we got it." So naturally I'm worried (because a prior shop had exactly said that before attaching that alternator wire!) I'll let you know.
Jack:
Because I started working on Land Rovers at the dealership during college summers and have been at it ever since, it is hard for me to understand why anyone would own an 80s 90s and older Land Rover who does not turn their own wrenches.

As Dale suggests, there are those publications that explain repairs and provide other data like wiring diagrams. Proper tools are available anywhere and good deals show up on Craigslist for used tools sometimes complete with large rolling cabinets.

Being self reliant is much better than being at the mercy of repair shops that often don't understand what they are working on, much less how to fix it. Yes there are good shops with specialists like Trevor, Matt, Pendy, and so on - but there are bad ones as well that have no clue.

Hope this helps and good luck.
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UD: "Just Power through it man!"
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  #10  
Old January 22nd, 2014, 08:43 AM
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Well said on all counts Robert!! Btw Vegemite arrived for ya!
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  #11  
Old January 22nd, 2014, 08:57 AM
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Hello Richard

Short answer: because of my loyalty to friends, mixed with some naivety.

I've been a car magazine & calendar photographer & writer for well over a decade, including traveling as a photographer for race teams & contributing to automotive books. During that course of time I built up friendships with great mechanics & car vendors. A few years back I thought I'd build the ultimate car photography vehicle. I polled these friends. They told me to get a Land Rover Defender. EVERY ONE OF THEM said if I bought one, they wanted to work on it. So I did & they have.

I also have the stupid or naive philosophy that, if a mechanic is helping me with something big, like fabricating AC pulleys & while in there he determines I need a new alternator, I say "Sure, go ahead & replace that too" rather than "No, I can do that, don't touch it."

Yes, I turn my own wrench & I have proper tools (in a rolling cabinet - with a Binford sticker on it!). But this wire is probably related to installing the 200 TDi in place of my 2.5 NA, & then adding a higher capacity alternator. Such an install could not be accomplished in my garage & I could find nothing in any manual or guide about that combination, hence my post.
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Old January 22nd, 2014, 09:29 AM
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Now that you have been properly censured by the Board of Directors, is it possible that you could include a pic of this mysterious wire?
To my limited knowledge, there should be only a brown or brown with orange (or maybe it's red) tracer coming from the alternator. The other wires are the excitation wire (wired onto the big brown wire), the idiot light wire and the tach wire.
As per this fine web-poached image below:

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Old January 22nd, 2014, 09:53 AM
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Thanks Bill
That does help
I hope to have a photo of mine to post by this afternoon.
Regards
Jack
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Old January 22nd, 2014, 09:58 AM
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Quote:
Originally Posted by Axel View Post
Hello Robert Short answer: because of my loyalty to friends, mixed with some naivety...
OK excellent.

As Bill helpfully suggests, showing a picture of the wire will go a long way to understand what is what with the black wire.

Question for Bill: What tool are you using to write over the photos? Snag-it?


Quote:
Originally Posted by Jonesy View Post
Well said on all counts Robert!! Btw Vegemite arrived for ya!
Can't wait to add that to the next party snack table, thanks.
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Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)

"What's with this death wobble, Uncle Douglas, I can't keep it in 1 lane?"
UD: "Just Power through it man!"
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Old January 22nd, 2014, 11:01 PM
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black wire from alternator

The black one which burned up was replaced by this thick copper ground cable, in clear sleeving, shown at the bottom of this photo of the back of my alternator. Out of the frame of the photo, it attaches to the frame.

At least the replacement fixed the problem & it runs fine. But it's still odd that, as a ground cable, it would arc & need sleeving.
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  #16  
Old January 22nd, 2014, 11:07 PM
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Unless I'm looking @it wrong is that some sort of ground from the mounting bracket bolt! Funky....
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Old January 22nd, 2014, 11:09 PM
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Quote:
Originally Posted by Bill Larson View Post
Unless I'm looking @it wrong is that some sort of ground from the mounting bracket bolt! Funky....
I agree with Bill. It is completely unnecessary in my book.
I don't have any wires going from my alternator to the frame.
B+ goes to the battery
D+ goes to the dashboard alternator light

Thats it.
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  #18  
Old January 23rd, 2014, 08:56 PM
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That is a PO ground...

Jack;
The pictured location is simply where some PO decided to connect your ground cable.
If it's the only ground cable then it is necessary,
BUT
The ground should actually go between the frame and the transfer case or gearbox and if this is not present or not making continuity, then this new ground cable is needed.
OR
If you have the continuity between the frame and the transfer case or gearbox with a different (-) ground, this cable in the picture is completely redundant.

The good news is, either way, this cable hurts nothing and can only help with (-) grounding although there are much better locations for a (-) ground.

Hope this helps.
Robert not Richard because I'm not a dick (at least not always)
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RDavisinVA

Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)

"What's with this death wobble, Uncle Douglas, I can't keep it in 1 lane?"
UD: "Just Power through it man!"
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  #19  
Old January 24th, 2014, 10:01 AM
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Thanks everyone.
At least I now don't feel as much of a dufus since I'd guessed right that there's not supposed to be a ground wire there - it just didn't make sense. But why this one has to be shielded is still strange. Maybe it was arcing to another wire on the back of the alternator.
I was wondering if this wire was something unique to transplanting a 200Tdi.
Thanks to your comments I'll check to see if I have the preferred ground between frame & transfer. At least it's running great now, thanks to the mystery wire & defendersource
Regards
Jack
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