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-   -   I would like a GOOD GOUND for my Alternator (

DuaneD 06-23-2007 06:34 AM

I would like a GOOD GOUND for my Alternator
Swapping in a 94 4.0 motor into my CJ has taught me a lot. One of the last things I want to do with the motor is create a seperate ground for the stock alternator. Where on the alternator should I connect the ground wire and where should I run it to...the frame, engine mount, straight back to the negative terminal of the battery, where? Thanks for the help.

SilentBob2 06-23-2007 08:34 AM

Why are you have to make a seperat ground ? I geuss Im missing something, the alternator should be grounded through the brackets and just run a heavy ground from the motor to the frame... I have allways used a battery cable for my grounds, easeir to find then them big heavy duty straps that my local parts store never seems to have in stock...

DuaneD 06-23-2007 10:06 AM

Good Question. Not having proper grounds on the PCM and computer for my 4.0 transplant have been the most important thing in getting the engine to operate correctly. Not having well connected or available grounds have taught me more that anything during my engine swap. Since the altenator is the energy heart to operate all the a-zillion amp hungry stuff in my Jeep, I don't want to take any chances, hence I want to be dog-gone sure I have the best possible ground for that enrgy producing device. Thanks.

P.S. I took me months (my bride would say years, hehehe,) to sort out a 94 OEM YJ wiring harness to get just what I needed to mate it over to my 85 CJ.

TiminMb 06-23-2007 11:56 AM

I'd run it from a bolt on the body of the alternator right back to the negative terminal of the battery. I have a ground cable from the negative terminal to a bolt through the firewall where I have a second cable to the dash (metal dash on a cj). It might be overkill, but who could fault someone having separate grounds to the block, grill, firewall, dash, starter solenoid, alternator? If you have the time, go for it. A common brass terminal on the firewall might be a good place to branch out from for smaller secondary grounds, and I'd run a heavy separate one to the block and alternator.

LEVE 06-23-2007 12:39 PM

Amen......:beertoast: :goodpost:

Junk Yard Genius 06-24-2007 12:10 AM

We've been preaching this for years!

Here is the scoop,
Electrically speaking,
You are driving several jeeps in very close formation, but none of them actually connected...

Loose fasteners, rust, mud, paint, ect. all conspire to keep your jeep from grounding correctly.

The reason your jeep didn't come with dedicated ground wires was...
It would probably cost $3 extra dollars at the factory to add proper grounding, but the factory thought that was too much.
And once your jeep made it through the 12 month warranty period, grounding problems were money in the bank!
Either you paid to have them fixed, or you paid to buy a new vehicle...

On your alternator problem,
Use at least a 10 gauge wire, run it from the alternator housing to the primary ground...
In your case, that will probably be your negative battery terminal connector.

As you have found out, PROPER grounds are few and far between.
Here are some things you might do to insure a proper ground and power system...

Now, from your binding post, you can run as many grounds as you need too...
Like one to the dash, one to the tail lights and fuel tank, one to the ignition module and engine block...

If you live in a wet area, DO NOT use woven ground straps.
They are open to everything the environment can throw at them and don't fare very well.

For battery cables, use at least a 4 gauge fine strand wire, or 2 gauge 'battery cable'...
An excellent wire to use for battery cable is welding cable.
Welding cable is fine strand, carries more current and is easier to bend and shape.
Welding cable is usually virgin copper, no alloys, so it will carry more current for the size of wire and will solder or crimp better.
Welding cable is easy to acquire, even NAPA sells it.
Welding cable has a rubberized insulation that is resistant to abrasion, chemicals, heat... All the things you find under a hood.
Welding cables will fit into any of the common battery terminals...
I recommend the sold copper, lead cadmium plated, crimp on style battery terminal connectors NAPA (and others) sell.
They are the correct size and shape, are much sturdier than lead terminals, and have the correct type of stainless steel battery bolt.

When you terminate your wires, use a solid copper terminal.
Some will be lead or nickle plated, and that's OK, but the base metal should be copper, not steel or lead!

Crimp on these terminals, then solder them down.
Crimping is only a MECHANICAL connection, solder is an electrical connection...

Don't forget to use glue fill heat shrink tubing!
This seals out the elements to make your new cables and wires darn near impervious to the elements!
Different colors of heat shrink will show color-coding for positive and negative, as well as some different colors for wires, like the feed to the alternator after the fusible link...
(Helps keep the harness straight in my head)

CJ7Taz 06-24-2007 03:03 PM


Originally Posted by Junk Yard Genius (Post 1508215)
On your alternator problem,
Use at least a 10 gauge wire, ...


Originally Posted by Junk Yard Genius (Post 1508215)
For battery cables, use at least a 4 gauge fine strand wire, or 2 gauge 'battery cable'...

Not near big enough on either.


Originally Posted by Junk Yard Genius (Post 1508215)
Welding cable is fine strand, carries more current ...
Welding cable is usually virgin copper, no alloys, so it will carry more current for the size of wire ...

I’m gonna need a reference on this one. I’ve been doing electrical for a lot of years and I’ve never heard of this. I think its more likely some bad conclusion jumping.

Comparing the ampacity for copper wire to the ampacity chart for welder cable, it would seem that welder cable is indeed higher than copper wire. The problem lies in using the wrong table for the copper wire, another table for wire in free air and comparing at the 90 temperature as in the chart for the welder cable, the ampacity increases. The welder cable chart has length limits, the copper wire chart does not.

To the side in the welder cable chart, there is another table given for 600V applications, the same voltage as the copper wire rating. Note that the ratings for welder cable are now lower than for wire in free air, but also note that the ratings for the welder cable are given at 40 ambient temperature. The NEC Table 310.17 wire ratings were as stated, “Based on Ambient Air Temperature of 30C." Below the table is a correction factor table for the higher temperature.

Now, we could make it difficult try to determine the temperature where the wire is or just use the enclosed conductor chart. 6 AWG will get you up to 140 amps or better for your alternator. If it’s only 85 amps, you COULD get by with 8 AWG. If you drop down to 10 AWG figuring that the alternator bracket, through the engine to ground will carry most of the load, you might want to read the Fire Extinguisher Mounting Options thread. For battery cable, I like at least 1/0 (one aught), 2/0 if I can get it.

The wire or welding cable is up to you. My jumper cables are welder lead mostly because they were free (cut out of an old cable with insulation cuts) but they also easy to handle and roll into a nice small loop for storage. Welder cable is easier to form but also doesn’t hold its shape so it has to be supported every few inches.

jeeperjohn 06-24-2007 04:56 PM


Originally Posted by Junk Yard Genius (Post 1508215)

Not to hijack the thread, but what do you use to make these diagrams?

RRich 06-24-2007 05:46 PM

Well there you have it! He He - Now you can build the entire watch from welding cable! Thanks TAZ.

Most of the "store bought" battery cables sold by AutoChina etc are 8, or even 6 gauge. According to Taz's chart they won't work at all.

Many jumper cables use only 10 Ga wire - with really thick insulation to scam you into thinking they'll work on Taz's 600 volt alternator. They don't work either, according to the chart.

Welding cable works fine!

CJ7Taz 06-24-2007 06:10 PM

Must be a California thing, more greenie stuff. Here, Ive never seen battery cables smaller than 4 AWG at AutoZONE or ADVANCED Auto, I can always find 2 AWG and sometimes 1/0. Doing a quick check, 4 AWG is the smallest I found on the AutoZONE website. If I were going to the trouble to build my own cables, theyd be 2/0.

Your dyslexia is kicking up again. That 600 volts is the wire insulation rating of most all wire.

Were too smart here to buy 10 AWG for jumper cables. I found some on a clearance table. Once you separate em, they make great jumper WIRES.

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