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Old 24-09-2008   #1
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Electrical earth/ground problems - How it happens.

This is a simple explanation of how poor electrical 'grounding' , also known incorrectly as 'Earth's occur , their symptoms and their cure.

To start , heres off some simple circuit theory.

Fig 1. Power goes from the battery , through the fuse , through the switch (when ON) through the device (in this case a lamp) and returns back to the negative terminal of the battery.

It is called a circuit because the electricity flows in a circle around the circuit.

If the circuit is broken at any point , current will not flow and it wont work.

In figure 2 it is the same circuit , but instead of a wire being used to make the circuit complete , grounds are used.
In car use , these grounding points are metal parts on the body.
The body metal is conductive to electricity , so this replaces the removed wire.
The circuit is still complete and every thing works properly.

Car manufacturers save money on wire doing it this way.

Figure 3 shows a more complicated circuit with many switch and globes.
If you trace the current path as each switch is closed in turn you will see that all globes light as intended.

Of primary interest in this example is the lower lamp circuit in Fig 4.
The electricity flows correctly through the switch , the lamp , and to the ground (back to the battery) and the lamp will light as it should.

In this Fig 5 we simulate a bad or broken ground point.
When we turn our lower lamp on power flows through the switch , through the globe but instead of it going to the ground as intended it cant.

Instead the current will try and find another path to ground if there is one.

We can see by following the arrows that the electricity flows through the bottom globe , through the second globe on another circuit , through yet another globe filament and then on to ground. Whew !.

The result in this example is 3 lamps dimly lit when the bottom switch is ON.
The two top lamps should not be lit at all , but they are now part of the first circuits ground path.

You may see cars occasionally that have their stop of park lights flash in time or opposite to the turn signal , or some other weird combination of unintended (often dull) lamp lighting events.

This is ALL down to one bad Ground connection.

The solution , Go through all of the ground connections in the area of the car that you suspect the problem to lie.
Often rear lamp Ground problems can be found near the actual lamps themselves - sometimes its a bit more involved to find the faulty ground point.

Grounds are most often damaged by rust or corrosion under the grounding point where it connects to the body.

Uno's make use of 'star grounds'. (aka sun grounds)
'Star grounds ' is just a fancy pants name for a piece of metal , usually round with many male spade connectors on it. (an easy to find example to see is just behind the headlights on the inner wheel arch)

These must have a clean metal contact under it for it to work.
Likewise ALL the female spade connector should be free of corrosion and firm fitting onto the ground point.
A thin smear of 'conductive grease' under the star connection to the body will pass current , yet resist future corrosion.

Sometimes if you are lucky , a ground wire has accidentally fallen off the ground point , it can be that simple , yet cause a lot of concern.

Thanks randomspeedfreak, Louie Bee, Chas Uno thanked for this post
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Old 25-09-2008   #2
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Re: Electrical earth/ground problems - How it happens.

A useful guide - thank you

Quote Originally Posted by Trinity View Post
we got a lot 126 here in Egypt .. a funny car and fun to drive though sometimes i feel like I am sitting on a chair in the middle of the street
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Old 25-09-2008   #3
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Re: Electrical earth/ground problems - How it happens.

Quote Originally Posted by 1986Uno45S View Post
A useful guide - thank you
Thanks for the kind thought

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Old 25-09-2008   #4
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Re: Electrical earth/ground problems - How it happens.

Yer makes sense, but never thought of it that way before really!

Thanks for taking the time out .
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