braided Earth Wire

[angus99]

Trying to resolve an earthing problem at the moment. Problem appears to be at the chassis bolt on the passenger side just in front of the gear shift. Gigling the battery negative, which is earthed to this point, can cycle power on and off.

Removed the battery negative lead, which I'm going to replace, but noticed that the conector on the braided earth wire seems to be burnt out. Anyone know what this wire is for? Traced it behind the dash and it appears to go into the engine bay.

[spend]

Some twerp has added an earth, like a certain guru has kept advising over the years... Problem is that if your main chassis earth fails..... the starter et al tries to find a path through those piddly wires and results in melted chaos.

I would advise that you never take any additional ground back to the battery unless you fuse it. If you are going to replace the main battery ground take a cable from the battery to the chassis as is and then consider adding daisy chain another section so that it is electrically connected to both chassis bolts either side of the transmission tunnel

[angus99]

The braided wire looks factory fitted to me as it runs though the loom under the dash. put a new connector on it and replaced the main earth lead and everthing is now fine. Also changed the plugs and the car now starts perfectly.

[Bassfiend]

spend said:

I would advise that you never take any additional ground back to the battery unless you fuse it.

Are you *REALLY* sure on this Spend?

I was always taught that grounds / earths should *NEVER* be fused (but should of course be of sufficient gauge to handle the maximum possible load that they can be asked to handle).

Phil

[Simon says]

I remember the time when losing the main chassis earth to engine block meant that when you next cranked the car over the throttle cable & choke cables smouldered nicely as they was the only source of earthing with neither being man enough obviously pre EFI cable failure shortly after where the cable had melted the inner liner was certain had a few of these to change in my earlier years

Edited by Simon says on Monday 2nd January 11:16

[Ribol]

Simon says said:

I remember the time when losing the main chassis earth to engine block meant that when you next cranked the car over the throttle cable & choke cables smouldered nicely as they was the only source of earthing with neither being man enough.............

So you worked on a lot of Minis then

[spend]

Bassfiend said:

Are you *REALLY* sure on this Spend?

I was always taught that grounds / earths should *NEVER* be fused (but should of course be of sufficient gauge to handle the maximum possible load that they can be asked to handle).

Phil

Well think about it.... if you lose the main earth cable (which is pretty hidden & unaccessable on a TVR compared to the 6-12" visible connection to body on a normal car) then every additional ground to battery is likely to have starter ampage... All you've stated is that your perceived wisdom dictates by implication installing battery cable everytime? What I said was that I advised you fused any additional earths to ensure you don't melt / burn wiring if there is a fault with the main earth - and that you take extra special care to ensure that the battery to ground connection is extremely good in the first place.

Personally thats why I always duplex my chassis grounds together with battery cable (from the battery under the trans tunnel, at the front under the rad and rear behind the tank) and add a additional short length to a stud in the fibreglass to link the harness to (then you can see the state of them and test easily) rather than clamping them directly to the chassis. I also like the symmetry of having electrical fields flowing equally around my chassis rails rather than ionising just one side

[Bassfiend]

spend said:

Well think about it.... if you lose the main earth cable (which is pretty hidden & unaccessable on a TVR compared to the 6-12" visible connection to body on a normal car) then every additional ground to battery is likely to have starter ampage...

Hmmm ... no ... not really. The only way for that to occur is if there's a parallel "earth" that isn't actually an earth.

For example a stereo ground would only get "starter amperage" through it if somehow the engine block was connected to the stereo's cage which simply should not happen.

spend said:

All you've stated is that your perceived wisdom dictates by implication installing battery cable everytime?

No - just appropriately rated for the load that is on it. Production cars don't have fused earths (as far as I am aware - perhaps I'm wrong and I'm sure that someone will correct me if I am) but having a fused earth where the fuse has "blown" in the earth connection will leave the device floating "high". I can't think of any electrical circuits where it would be valid to have the supply current remain intact when the return path was blown.

spend said:

What I said was that I advised you fused any additional earths to ensure you don't melt / burn wiring if there is a fault with the main earth - and that you take extra special care to ensure that the battery to ground connection is extremely good in the first place.

Hmmm ... I can kind of see your point but in fusing the earths all you're doing is layering up possible issues. I'm sticking with "earths should never be fused"...

spend said:

Personally thats why I always duplex my chassis grounds together with battery cable (from the battery under the trans tunnel, at the front under the rad and rear behind the tank) and add a additional short length to a stud in the fibreglass to link the harness to (then you can see the state of them and test easily) rather than clamping them directly to the chassis.

All perfectly sensible precautions...

spend said:

I also like the symmetry of having electrical fields flowing equally around my chassis rails rather than ionising just one side

LOL

Phil