Split Earth
turnipfarmer - 23/5/23 at 01:45 PM
Hi guys...
A few days ago I came across a single earth wire that was being used to earth 2 different pieces of kit by means of a 'Y' lead.
(I've changed this so both items now have their own separate earth wires.)
But it set me thinking... what if I had left it as it was and then:
One of the earths on the 'Y' lead became loose and wasn't serving its purpose?
What effect (if any) would that have on the piece of kit on the other part of the 'Y' lead? Would that be compromised?
Can't seem to find a definitive answer to this one. Anyone out there know?
loggyboy - 23/5/23 at 02:19 PM
Is this post serious?
If so and your playing with wiring please stop and take the car to someone who knows more.
This is GSCE physics.
gremlin1234 - 23/5/23 at 02:52 PM
bad earths can give all sorts of problems, most usually on rear lights that seem to do bizarre things, like the side light going out on one side as
the indicators flash.
but generally it is fine to use common earthing.
however, with the increase in sensors in cars, it is now best practice to run a dedicated signal ground from the ecu to each sensor.
[Edited on 1 by gremlin1234]
adithorp - 23/5/23 at 05:41 PM
Shared earth see perfectly normal. Not a problem as long as the shared cable is capable of carrying the current from all the circuits. A rear lamp
cluster for instance will have several bulbs sharing one earth.
If one earth in your example became disconnected, then that circuit would no longer work. There would be no effect on the still connected one.
Earth faults, as described by gremlin1234, happen when there's a problem with the shared earth and the current in one live circuit finds an
alternstive route to earth through another circuit. Common on rear lights where each side has its own shared earth; One earth connection fails (after
the common junction) and the current from (for example) the brake circuit feeds back through the sidelight bulb, via the shared earth, through its
live side to the opposite cluster, then through that sidelight to earth on that side.
coyoteboy - 23/5/23 at 10:08 PM
quote:
Originally posted by loggyboy
Is this post serious?
If so and your playing with wiring please stop and take the car to someone who knows more.
This is GSCE physics.
Sort of, but that's a bit harsh to say the least. Apart from anything it depends how the grounding scheme is laid out and where they're
talking about. Sure a split ground off the battery negative is "obvious" but there are configs where if thus was a poor description it might
render a few issues. Never take the mick out of someone trying to learn.
Mr Whippy - 25/5/23 at 06:01 AM
quote:
Originally posted by loggyboy
Is this post serious?
If so and your playing with wiring please stop and take the car to someone who knows more.
This is GSCE physics.
A very disappointing reply and not at all in the spirit of this forum...
Mind your whole car frame or shell is a shared earth. Most cars have many items sharing both positive and negative and is a good way to reduce the
amount of wiring. Electrics is a weird subject and many folk struggle with it. As above never discourage people from trying to learn something new
even if the answer many seem obvious to you.
adampage - 30/5/23 at 09:19 AM
....and can't spell GCSE.... 
Furthermore, it should say "you're" not "your" while we're at it.....
Not very nice having your post criticised is it?
Agree with Coyoteboy & MrWhippy, no need for that response was there, always good to ask questions, and as has been pointed out it's not even
that unusual.
----------------------------------------------------------------------------------------------------------
Originally posted by loggyboy
Is this post serious?
If so and your playing with wiring please stop and take the car to someone who knows more.
This is GSCE physics.