Great that it’s running now, but I’d love to know what caused that wire to burn out (as I’m sure you are!)…
Did it seem that it was nothing to do with the changing of the battery and connectors? Could it be that some other wiring was disturbed or chaffed against the chassis causing the short?
No wonder it didn’t start with something shorted to the chassis (most likely I guess), but be nice to know how it occured.
Keep us posted, but guess we won’t know until after the turkey now!
Alex,
Yes having done some ringing round a couple of auto electricians have told me that if i had a faulty earth connection to the battery that it would cause a short on the guilty earth lead in to this connector! All seems ok now though, having taken the battery out, refitted it and taped up the offending wire!
A local lad called Nath popped over with his ‘new’ S1 Exige but i couldnt find this connector and series of wiring on his…yet Tim who was the first owner would definately have told me if that area had been modded or altered so im a bit confused, especially as he nearly had a heart attack when he heard about this fault!
Yes having done some ringing round a couple of auto electricians have told me that if i had a faulty earth connection to the battery that it would cause a short on the guilty earth lead in to this connector! All seems ok now though, having taken the battery out, refitted it and taped up the offending wire!
Sounds plausible. Poor little wire acting as the earth for entire the cranking current. No wonder it melted!
Think the neg of the battery is meant to be bonded to the chassis somewhere… Worth checking this is OK.
The reason you may not have seen it on Nath’s car (aside from any A/C, non A/C differences) might simply be the differences in build with low volume hand built sportscars. ie. no two are exactly the same!
Poor little wire acting as the earth for entire the cranking current. No wonder it melted!
If the negative cable from the battery was not earthing properly then there can’t be a circuit to the battery and the engine would not crank would it?
Exactly!!! I couldnt get the engine to crank, yet smoke billowed from said area…once i removed the battery and refitted it very carefully, it cranked no problem!
Yes having done some ringing round a couple of auto electricians have told me that if i had a faulty earth connection to the battery that it would cause a short on the guilty earth lead in to this connector! All seems ok now though, having taken the battery out, refitted it and taped up the offending wire!
Sounds plausible. Poor little wire acting as the earth for entire the cranking current. No wonder it melted!
Think the neg of the battery is meant to be bonded to the chassis somewhere… Worth checking this is OK.
The reason you may not have seen it on Nath’s car (aside from any A/C, non A/C differences) might simply be the differences in build with low volume hand built sportscars. ie. no two are exactly the same!
All part of the fun. Glad all seems well now.
Yep, checked all of that.
Good point about no two cars are the same, i never thought of that!
And i agree, poor little wire taking all of the current…could this be the case and now all of the earth points are secure do you think it should be okay now?
Poor little wire acting as the earth for entire the cranking current. No wonder it melted!
If the negative cable from the battery was not earthing properly then there can’t be a circuit to the battery and the engine would not crank would it?
Exactly!!! I couldnt get the engine to crank, yet smoke billowed from said area…once i removed the battery and refitted it very carefully, it cranked no problem!
Sorry didn’t make myself clear - if the earth off the battery is not connected properly then I don’t see how any major circuit can draw current - the starter motor has its own earth.
Could it be that the starter didn’t crank because there was a huge open circuit elsewhere and electricity takes the path of least resistance.
If reconnecting the battery made a real difference then there could not have been any current being pulled beforehand and so no chance of the fire.
Are there any burn marks around the positive terminal of the battery, ie, did it short out on something - is the battery loose?
Well glad to see it is running. I do like the idea of a dodgy earth to the battery, so the earth in question is taking all of the load.
The main earth from the battery to the chassis is bolted to the chassis on the passanger side at the front of the tub low down on the main chassis rail. It is worth seeing if that is tight. As you removing and refiting the battery, may have moved the wire so that it is now making a circuit, but it could obviously move again if not tight.
The main engine earth goes from the gearbox to the passanger side chassis rail just to the side of the gearbox. It would be worth checking that the bolts holding each end of that are tight too.
Well glad to see it is running. I do like the idea of a dodgy earth to the battery, so the earth in question is taking all of the load.
Chaps,
Having done yet more research it looks like the it WAS a dodgy earth with the much smaller earth taking all of the load when trying to crank the engine over, therefore heating up and burning out!
It seems that this could be the earth to the starter motor, would that make sense, and as it was taking ALL of the load when trying to start the car and just burnt itself out!
Now that all of the earth points have been checked and the ‘faulty’ earth re-covered with electricians tape all should now be ok?
I guess i have you misunderstood here. But there is no earth wire to the starter. The big thick wire on the starter is a live and the thin one switches the starter solenoid. The starter earths through its mounting on the gearbox. So you need to check the earth strap that goes from the gearbox to the chassis rail and the earth strap from the chassis rail to the battery.
Having done yet more research it looks like the it WAS a dodgy earth with the much smaller earth taking all of the load when trying to crank the engine over, therefore heating up and burning out!
It seems that this could be the earth to the starter motor, would that make sense, and as it was taking ALL of the load when trying to start the car and just burnt itself out!
I think you have this wrong - the circuit is made by both the starter earthing via the gearbox earth strap to the chassis AND then the chassis back to the battery to complete the circuit via the battery negative terminal connection to the chassis, ie, a full circuit pulls the current through both earth leads and not just one or the other.
If the starter motor is not earthing properly then the starter will not crank or pull any current - it needs a complete circuit to work, break the circuit in any one place the the current will not be drawn.
Clearly, you were drawing current to start the fire, therefore the battery earth connection to the chassis must have been good.
Earth cables do not need covering in tape - traditionally they are flat ribbon braided steel cables. Electricity takes the path of least resistance. For a test (not really recommended) undo the positive terminal of the battery before the negative and allow the spanner to come into conntact with botht he nut on the terminal and any other metal - its not fun! Conversely, try the same with the negative terminal and nothing happens.
That’s why you always disconnect the negative terminal 1st and reconnect last.
I guess i have you misunderstood here. But there is no earth wire to the starter. The big thick wire on the starter is a live and the thin one switches the starter solenoid. The starter earths through its mounting on the gearbox. So you need to check the earth strap that goes from the gearbox to the chassis rail and the earth strap from the chassis rail to the battery.
Sorry Sean, asa you probably realise everyone you speak to always knows best so im sorry if that information was duff, but I reckon its definately an earth problem…if there was a fault on the main earth cable to the battery would that result in this smaller earth taking all of the load and therfore ‘smoking’?
Yes it could happen that way. As Steve says there needs to be a complete circuit for the car to crank, but say if the main earth from the battery to the chassis is not connected at the chassis end, but there are other smaller earth wires going to the negative terminal of the battery, then yes if it can find a way it will. I have seen cars that do not have enough engine earths and they earth through things like braided hose and the throttle cable. Obviously there is a HUGE current draw when the engine is cranking, hence why this could be the reason the thin wire over heated.
Having done yet more research it looks like the it WAS a dodgy earth with the much smaller earth taking all of the load when trying to crank the engine over, therefore heating up and burning out!
It seems that this could be the earth to the starter motor, would that make sense, and as it was taking ALL of the load when trying to start the car and just burnt itself out!
I think you have this wrong - the circuit is made by both the starter earthing via the gearbox earth strap to the chassis AND then the chassis back to the battery to complete the circuit via the battery negative terminal connection to the chassis, ie, a full circuit pulls the current through both earth leads and not just one or the other.
If the starter motor is not earthing properly then the starter will not crank or pull any current - it needs a complete circuit to work, break the circuit in any one place the the current will not be drawn.
Clearly, you were drawing current to start the fire, therefore the battery earth connection to the chassis must have been good.
Earth cables do not need covering in tape - traditionally they are flat ribbon braided steel cables. Electricity takes the path of least resistance. For a test (not really recommended) undo the positive terminal of the battery before the negative and allow the spanner to come into conntact with botht he nut on the terminal and any other metal - its not fun! Conversely, try the same with the negative terminal and nothing happens.
That’s why you always disconnect the negative terminal 1st and reconnect last.
Please accept my ignorance Steve but what would be the outcome if say the earth was not connected to the battery but somehow was touching the chassis instead…maybe it wasnt the starter motor I was hearing but when i turned on the ignition it certainly sounded like it was trying to start, then this smaller earth burnt out…is it possible that this smaller earth wire was making the circuit and that the main earth could have had a break in it somewhere???
Having done yet more research it looks like the it WAS a dodgy earth with the much smaller earth taking all of the load when trying to crank the engine over, therefore heating up and burning out!
It seems that this could be the earth to the starter motor, would that make sense, and as it was taking ALL of the load when trying to start the car and just burnt itself out!
I think you have this wrong - the circuit is made by both the starter earthing via the gearbox earth strap to the chassis AND then the chassis back to the battery to complete the circuit via the battery negative terminal connection to the chassis, ie, a full circuit pulls the current through both earth leads and not just one or the other.
If the starter motor is not earthing properly then the starter will not crank or pull any current - it needs a complete circuit to work, break the circuit in any one place the the current will not be drawn.
Clearly, you were drawing current to start the fire, therefore the battery earth connection to the chassis must have been good.
Earth cables do not need covering in tape - traditionally they are flat ribbon braided steel cables. Electricity takes the path of least resistance. For a test (not really recommended) undo the positive terminal of the battery before the negative and allow the spanner to come into conntact with botht he nut on the terminal and any other metal - its not fun! Conversely, try the same with the negative terminal and nothing happens.
That’s why you always disconnect the negative terminal 1st and reconnect last.
Please accept my ignorance Steve but what would be the outcome if say the earth was not connected to the battery but somehow was touching the chassis instead…maybe it wasnt the starter motor I was hearing but when i turned on the ignition it certainly sounded like it was trying to start, then this smaller earth burnt out…is it possible that this smaller earth wire was making the circuit and that the main earth could have had a break in it somewhere???
Sorry chaps, I think Sean has just answered this question above!
Yes it could happen that way. As Steve says there needs to be a complete circuit for the car to crank, but say if the main earth from the battery to the chassis is not connected at the chassis end, but there are other smaller earth wires going to the negative terminal of the battery, then yes if it can find a way it will. I have seen cars that do not have enough engine earths and they earth through things like braided hose and the throttle cable. Obviously there is a HUGE current draw when the engine is cranking, hence why this could be the reason the thin wire over heated.
Okay so if that was the poroblem and i have now checked all of the main earthing points and they look good, should everything be ok now and is there likely to be any lasting damage caused?
Mr B - not setting myself up an an auto electrician, but owning an old landrover for 22 years has meant I have learnt the hard way on chasing and fault finding electrical problems - many to do with poor earthing.
Please accept my ignorance Steve but what would be the outcome if say the earth was not connected to the battery but somehow was touching the chassis instead.
For the earth to work it has to be connected to both the battery negative terminal and the chassis. The chassis takes the place of running a cable back from every electrical item directly to the battery. If the earth cable is loose or not making a “good” connection at either the battery or chassis end then no electrical item should work. In practise, these things are never black and white, so a circuit drawing a small amount of power, say an interior light, may work but those items, such as starter motors, which draw a large amount of current will not work.
when i turned on the ignition it certainly sounded like it was trying to start, then this smaller earth burnt out…is it possible that this smaller earth wire was making the circuit and that the main earth could have had a break in it somewhere???
It may be simplistic but if you have a problem on the earth or return side then usually things just don’t work. Sparks, bangs, smoke, smells, etc are normally associated with problems on the live side of the circuit.
Its more likely from what you say that the starter motor did start to turn, then the short circuit somewhere else kicked in, stopping the starter and drawing enough current to create the fire.
Ive traced it to a connector which houses four wires that sits just in front of the brake fluid resevoir, it looks like the earth has burnt itself out, I cant find out where these wires end up or what they are for…could it be the cooling system?
Just re-read this - no mention of blowing any fuses or have I missed a post?