Register Login
Shop4Parts - UK's largest online superstore for FIAT and Alfa Romeo parts
Reply
 
Thread Tools
Old 24-09-2008   #1
Join Date: Sep 2008
Posts: 70
Thanks: 9
Trader Rating: 0
Finland 
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.

gW:-)
Thanks randomspeedfreak, Louie Bee, Chas Uno thanked for this post
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides | FAQs

UNO-MK1 is offline Reply With Quote Quote 
Old 25-09-2008   #2
Classic Uno Obsessive
 
Chas Uno's Avatar
Join Date: Jul 2004
Location: Watford
Posts: 7,328
Thanks: 237
Trader Rating: 0
Chas Uno has donated!
Air Dodge Champion, Asteroids2000 Champion, Frogger Champion
United Kingdom 
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
http://onastick.net/drew/sinistar/
Chas Uno is offline Reply With Quote Quote 
Old 25-09-2008   #3
Join Date: Sep 2008
Posts: 70
Thanks: 9
Trader Rating: 0
Finland 
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

gW:-)
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides | FAQs

UNO-MK1 is offline Reply With Quote Quote 
Old 25-09-2008   #4
Fixin UnoTurbo I sleeper
 
Louie Bee's Avatar
Join Date: Oct 2004
Location: N.W.
Posts: 2,668
Thanks: 76
Trader Rating: 9
Louie Bee has donated!
Rollin X Pinball Champion, Bubble Bobble Champion
Mozambique 
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 .
__________________
Louie Bee is offline Reply With Quote Quote 
Reply
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump
Similar Threads
Thread Thread Starter Forum Replies Last Post
(G) Earth / Electrical fault - Seicento '03 Fix It Again Tommorow Cinquecento / Seicento 15 03-12-2010 07:46
(T) Electrical Problems aj287 Barchetta 8 04-03-2007 23:11
(T) ELECTRICAL: bad earth?? nickphonics18 Punto (Mk2/2b) 4 11-04-2005 09:51
(T) electrical problems??? nothappy Punto (Mk2/2b) 3 16-03-2005 01:16
(G) Electrical problems Splash9 Tipo 4 16-03-2004 18:38