Technical Main earth

[PeeQueue]

Hi all -

I recently purchased a 500L through a private sale and it’s caused no end of bother. I’ve potentially come to the conclusion that my woes are down to the main earth, as I’ve read that this is a common fault with Fiats. However, I’m confused as to whether the 500L is the same as a 500 - the 500 has 2 earth cables (the one coming from the battery to a bolt, and another coming from that bolt to under something to do with the clutch). When I’ve looked at the 500L it seems to just have one main earth cable, coming from the battery, connecting to a bolt half way along and then terminating at a bigger bolt onto the main frame of the car (I think - I’m a woeful amateur ). Could anyone possible confirm that the 500L definitely only has one ground cable from the battery? And if so, is it as prone to fault as the standard 500? Many thanks in advance for your help

 

[AndyRKett]

All cars have a ground cable.

Fiats tend to have a single cable with a connector in the middle. One end connects to the battery, the other end connects to the engine or gearbox, and the middle connects to the body of the car, usually just below the battery tray.

It may be better to explain the issues you are/have been having and so we can advise on that. You could otherwise spend ages messing about with wires that don't solve the problem as they were never the problem in the first place.

What year is the car. What work has it had done? mileage? what engine is fitted? give us all the Info then we can advise what to do.

 

[PeeQueue]

All cars have a ground cable.

Fiats tend to have a single cable with a connector in the middle. One end connects to the battery, the other end connects to the engine or gearbox, and the middle connects to the body of the car, usually just below the battery tray.

It may be better to explain the issues you are/have been having and so we can advise on that. You could otherwise spend ages messing about with wires that don't solve the problem as they were never the problem in the first place.

What year is the car. What work has it had done? mileage? what engine is fitted? give us all the Info then we can advise what to do.

Hi Andy -
Thank you for the reply! The reason I’m unsure is the 500 seems to have two bits to the main earth, the one deeper in the bowels being the one that seems to get a bit dodgy.

The issues I’ve been having are numerous! It all started on the day I purchased it. The seller was open about it needing to be jump started as it had sat around for a while. But once it was jump started all seemed fine, until it came to drive it home to Alnwick - the car being in Edinburgh. As soon as I got onto the motorway the revs would suddenly stop, the speedometer would zip down to 0 and the headlights would turn off and then all would zip back to normal, all in the space of half a second. The dashboard also started coming up with a glow-plug and engine fault. It was getting dark, so pulled over and waited for the AA. AA diagnosed a dodgy battery (which we knew) and gave the battery a boost which got rid of the flickering of the electrics and we got home. Organised a battery change with Halfords, which seemed to sort everything bar the glow plug light on dashboard. Arranged for a mechanic to look at it, but in the meantime drove car a short distance, stopped for a minute and tried to restart but it wouldn’t even turn over. Tried to jump start, and battery started leaking. Halfords agreed to swap battery, and they also cleared all faults which seemed to fix the problem again. Halfway back home the speedometer and odometer stop working completely. Got car to mechanic to sort glow plugs but they advised there was an electrical fault and advised having it seen to at an auto-electrician in case it was a write-off. Auto-electrician found a dodgy connection behind the fuse box in the bonnet of car, and a dodgy stop-start sensor on the negative terminal. They fixed the connection behind fuse box which sorted the speedometer but didn’t have the part for the stop-start - they advised that the car should still run fine without the stop-start sensor working. Arranged for car to go back to mechanic, but on the day car wouldn’t start again - battery was flat. Jump started it, we got it to the mechanic and they said the broken start-stop sensor would be getting in the way of charging the battery. Got replacement sensor/negative terminal - start/stop now working, but battery still not charging. Diagnosed dodgy alternator. Got alternator changed and car working fine. 2 days later, start car and engine fault comes up, start/stop not working and now, when putting the blowers on to clear the windscreen, the internal lights come on and a ‘door open’ warning comes up (which all turn off/disappear when turning off the blowers). And that’s where we are at. Battery isn’t flat yet, but not confident that won’t happen again. Research has shown that many of the faults I’ve experienced can be due to a dodgy earth.

It’s a 2013 500l, 1.3 diesel. Done about 159k miles. It was cheap, so possibly worth all the effort to get it working.

Thank you for any help you can offer - apologies for the tome!

 

[The Panda Nut]

As an example of earthing issues and how hidden they can be, I bought a MIG welder. Screw fix.... should have known better. It was only used once and it failed. Wrong metals used in the main cable, so the next time I tried it the cables had turned to dust inside the insulation. It looked fine, still brand new. But was as dead as a Do-do. I decided to scrap it for the bits. THe fault was only found when I wanted to recover the copper from the main cable. There wsnt any! Just dust. It wasnt copper anyway but appeared to have been aluminim mesh. If you have a new battery change the earth wire and clean the fixing points.

As you now have a welter of faults I think it must be damaged wiring. As you have door open sensors involved I would check wiring in the door hinge aea and tailgate area are still sound as the most likely potential weak spots as your next job.

Dont trust new parts to be good either, recheck they are actuall working. I have played with bad parts too many times on Fiats!

 

[AndyRKett]

The earthing issue that you have probably heard of usually is caused by a poor connection between the engine block and the body/battery of the car. Basically the whole car is the negative terminal of the battery, as is the metal of the engine. if the thick cable that comes down from the battery, then attaches to the body, then carries on and usually attaches to the front of the gearbox on a 1.3 multijet engine

The usual problem if this cable breaks down by the front of the gearbox is that the car will not start, as enough current cannot flow to turn over the starter motor.

It does not normally cause any of the issues you have highlighted, as it is only the ground that goes to the engine block. It would not effect other electronics in the car. By all means you can take a look at the cable. just follow the largest black wire from the battery negative terminal down to below the battery tray, where it attaches to the body of the car, then carries on down and you'll find it attached to the front of the gearbox somewhere just below the battery.

If it looks like it is broken in any way, then just replace it with an off the shelf earth cable from the auto parts shop. They are pretty cheap and easy to replace, though I suspect it will not in any way shape or form do anything to repair the problem you have.

Also make sure the battery terminals are nice and clean and make sure the connections to the battery are tight.

It may be the battery earth to car body connection is bad, I am not sure however this is your problem and I think plugging it into diagnostics might give you a better idea of what is going on.

 

[PeeQueue]

The earthing issue that you have probably heard of usually is caused by a poor connection between the engine block and the body/battery of the car. Basically the whole car is the negative terminal of the battery, as is the metal of the engine. if the thick cable that comes down from the battery, then attaches to the body, then carries on and usually attaches to the front of the gearbox on a 1.3 multijet engine

The usual problem if this cable breaks down by the front of the gearbox is that the car will not start, as enough current cannot flow to turn over the starter motor.

It does not normally cause any of the issues you have highlighted, as it is only the ground that goes to the engine block. It would not effect other electronics in the car. By all means you can take a look at the cable. just follow the largest black wire from the battery negative terminal down to below the battery tray, where it attaches to the body of the car, then carries on down and you'll find it attached to the front of the gearbox somewhere just below the battery.

If it looks like it is broken in any way, then just replace it with an off the shelf earth cable from the auto parts shop. They are pretty cheap and easy to replace, though I suspect it will not in any way shape or form do anything to repair the problem you have.

Also make sure the battery terminals are nice and clean and make sure the connections to the battery are tight.

It may be the battery earth to car body connection is bad, I am not sure however this is your problem and I think plugging it into diagnostics might give you a better idea of what is going on.

Thank you for this. At every step the car has been plugged into diagnostics and the last time it was plugged in, since the alternator was changed and the stop/start sensor replaced, nothing is coming up.

The earth doesn’t look broken in anyway, and the connection on the gearbox looks solid. But I’ve read that the clip that goes over the pole on the negative terminal is known to be a bit dodgy at times.

I’ve found a message board saying they had the same problem with the windscreen blower making the lights come on and that changing the earth fixed it. And another message board talked about how the engine light was coming on but it ended up being the earth at fault. Could they be talking about a different earth?

 

[PeeQueue]

Just found this very helpful guide on here: https://www.fiatforum.com/threads/the-electrical-gremlin-thread.318839/. Going to follow this through before replacing the cable and see what I get.