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Old 08-24-2006, 06:25 PM
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Negative Grounding? How does it work?

I am hoping to begin learning how to wire, for automotive purposes. I understand cars use negative grounding most of the time. This is a complete mystery to me, and I havent been able to find very much information on it. I understand it uses the negative battery terminal connected directly to the chassey, but how does it work in the circuit, or 1 wire lights....

Any explanation, or direction to detailed explanation (books, websites) would be great!

Thanks in advance!
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Old 08-24-2006, 06:43 PM
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well, basically grounding the battery - to the chassis make the chassis your path back to the battery, so everything you wire up will just be grounded to the chassis also. with one wire lights, the body of the light is usually the ground, so you need to make sure that your body is well grounded also, I usually like to implement a couple grounding straps form the body to the frame front and rear.
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Old 08-24-2006, 09:31 PM
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the red wire goes to the fusebox, and starter, and from there smaller wires go off to accessories (ignition, radio, lights, etc) and from there a short ground wire to the chassis.

note some Fords are positve ground (8n tractors, I believe a Merkur XR4ti (mustang svo) in particular)

*path of electricity*
-assuming red is positive, and black is negative, as the standard goes.

battery>large red battery cable>fusebox>smaller wire(s)>accessory>small black wire (usually black, sometimes device is grounded direct to chassis as most starters)>chassis>black battery cable>battery
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Old 08-25-2006, 12:20 AM
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Doc here,

NEGATIVE GROUND BUSS:

The main Idea of a proper GROUNDING system is to insure that all metal parts of the Vehicle are at the same Electrical potential. So If I apply a ground at the front of the car, it will have the same resistance as one applied at the rear when referenced back to the source (Battery).

A Circuit that has resistance, will not operate as well as one that does not. Even a tiny amount can for instance Dim lamps, and cause heating in the wire or connectors.

Most overlook grounding principals when troubleshooting gremlins with the mindset: "It's ground ..It's everywhere.." May be true..but May not be a good ground..and causing all kinds of "Intermittent" and poor performing end user devices.

Think about it..a Body is mounted on Rubber mounts..An Engine is mounted on rubber mounts, a Transmission is mounted on rubber mounts..All kinds of potential for bad/lost grounds there..AND ..I don't know about you..But (exaggeration.. ) I wouldn't want my Fuel line carrying the only solid ground for my starter at 650 CCA because everything else has isolated itself from ground.

To prevent that, and to have a trouble-free performing system This is the best way to achieve that:

Run a properly gauged Ground cable from the battery to any handy bolt at or near the starter on the Block. From that same bolt get a 4 ga or better Battery cable at the parts store that has two 3/8 ring terminals on each end and attach it as close as possible from there and to the Frame.



Next get some 10 gauge wire and ring terminals (or a ground Buss wire kit as shown) and run that from your bolt on the Engine block where the Cables were just Installed, to the Firewall, Drill, burnish and attach it there, and another to the Alternator bracket or mount bolt.



Next get a Roll of Wire Braid, (Radio Shack) , Or if you have some RG~8 Coax cable, you can slit the insulation off the Coax and remove and flatten the Braided outer connector, then Install ring terminals.

Install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body.

At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.

<---star washer<---Tech or Self Drilling Screws.

Wherever your wire bundle and cables pass close to a solid surface, Attach it using RUBBER Coated ADEL clamps. , properly sized to the cable.

If the Cables or Bundle must pass Through the Body or frame, use a proper Grommet, Glued to the surface, AND when the wires are routed, pot the center and Cable/Bundle With Electricians PuttyThis stuff is $2.00 a pound, stays ply-able forever, and will keep out Fumes, water, Fuel, Dirt, Grease and just about anything you can think of from passing through the grommet.

Where you must Bundle a main harness of ground wire, You can use Tie wrapsOr another nice option is Flexible Conduit (plastic tube with a side slit). An assortment of ties will run you about $15 bucks..The Conduit kit a bit more..

Where ever you must cut and splice a wire, I recommend Soldering, make a good mechanical connection, then flow in a good solder joint..Cover that with Shrink tubing. I like to do 2 sections, one atop the other..for longevity...

The same applies for Connectors..I use uninsulated Terminal connectors, Strip and tin the wire, then Tin the terminal, measure a bit of heat shrink (black) then another (usually color coded, Red, White..ect) To slide over the first and a bit shorter than the first..

Then keeping both tubes far back, Crimp the Wire to the terminal, Then Flow solder into the terminal/wire until it's nice and shiny smooth, let it cool, and slide the black tube over, shrink it, then the colored , shorter tube over that and shrink..Makes for a real pro looking/lasting job..AND I never had one fail!

Grounding Systems are the most overlooked system in an automobile..YET..they are EXACTLY 1/2 The circuit! If you lose power..what happens? The device quits working..If you lose ground..guess what?? It don't work either..

Usually under sized or under rated when added or molested or upgraded , sooner or later cause all kinds of problems that defy logic it would seem..

The Ground system is JUST as important as the Power Buss..

Also, all these procedures work equally well on a Power system or anywhere you need to wire..so It's handy to know..

Does that help you at all?

Doc
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Last edited by docvette; 08-25-2006 at 01:05 AM. Reason: I before E ..Except after a 12 pack..
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Old 08-25-2006, 12:49 AM
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Negative Grounding Explained: A Drawing

Perhaps this drawing will help.

You mention wondering how a light with just one wire works, so I used that as a drawing theme to explain negative ground - in very basic terms.

Asking questions like this is always good, ask all you need to.

Jon P
Attached Files
File Type: pdf Chassis Ground Explained.pdf (46.0 KB, 308 views)
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Old 08-25-2006, 06:50 AM
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Quote:
Originally Posted by ChevelleSS_LS6
note some Fords are positve ground (8n tractors, I believe a Merkur XR4ti (mustang svo) in particular)
Most old tractors are positive ground up until the late 50s or early 60s models. Our 1941 9N Ford tractor is still 6 volt positive ground. However our 1954 60 John Deere was a 12 volt negative ground originally (in 1961 John Deere went to a 24 volt system). Tractors are easy to change from 6 volt positive ground to 12 volt negative ground. I changed my 1954 Allis Chalmers from 6 volt positive ground to 12 volt negative ground last year and it even looks original since I used a 12 volt generator off of an early 60s Ford truck instead of an alternator. Our 1940 M Farmall was already converted to 12 volt negative ground when I bought it.

A lot of old cars were also positive ground but I could not tell you what makes or what years. I did not know any modern cars that were positive ground.
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Old 08-25-2006, 07:17 AM
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I read some where, that negative grounding slows down corrosion of the metal work, and that positive grounding speeds up corrosion.

I can't remember where i saw this, but could some one correct me if I am wrong.
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Old 08-25-2006, 07:48 AM
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Id like to thank all you for taking the time to give me this information!

Lots of help!

Hallam
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Old 08-25-2006, 10:38 PM
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Quote:
Originally Posted by CrashFarmer2
I did not know any modern cars that were positive ground.
my older brother had one a couple years back.. it was pretty cool, I'm pretty sure it was pos ground anyways, not 110% sure.
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Old 08-26-2006, 01:30 AM
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Quote:
Originally Posted by hallamwillis
Id like to thank all you for taking the time to give me this information!

Lots of help!

Hallam

Doc here,

No sweat..

Questions are how you learn ... as much as "Hands on"..

Doc
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