Technical What is this thing connected to my battery? (And why is it unplugged)

[oskin]

Hi folks! I’ve recently got a 2020 Fiat Ducato which to my dismay threw a check engine light on my drive home from from the seller.

I’m going down the route of MultiECUScan to identify the codes and potential solutions later today but in my rummaging around earlier I noticed that there’s a battery connection which is unplugged inside the battery compartment. As far as I know the previous owner had no additional electrics so I can only assume that this is part of the base vehicle and should be plugged in. I suspect maybe something to do with start/stop or perhaps a smart battery charger?

Can anyone help me identify this port and perhaps take a guess at what might be the effect if I plug it in? Any guesses at why it is unplugged are also welcome!

Could it even be related to my Check Engine light?

Thanks in advance!

 

[rayc]

I think it is a battery shunt that is used as part of the alternator charging system for the smart battery. Some owners disconnect it so that it does not inhibit alternator charge to the leisure batteries. I guess there is more to it than that and hopefully you will get a better technical, though simple to understand, explanation.
PS addendum: are you sure the disconnected socket is part of the shunt system which looks connected in your photo? I had the same unconnected socket flying lead on my last motorhome, a 2013 model, which did not have the shunt. The flying lead with the eyelet was connected to the battery positive terminal???

 

[oskin]

I think it is a battery shunt that is used as part of the alternator charging system for the smart battery. Some owners disconnect it so that it does not inhibit alternator charge to the leisure batteries. I guess there is more to it than that and hopefully you will get a better technical, though simple to understand, explanation.
PS addendum: are you sure the disconnected socket is part of the shunt system which looks connected in your photo? I had the same unconnected socket flying lead on my last motorhome, a 2013 model, which did not have the shunt. The flying lead with the eyelet was connected to the battery positive terminal???

Hmm yes I think you're right. The smart alternator relay appears to be plugged in correctly and this wire is actually unplugged from the positive terminal.

So I have:
1) A loose lead with an eyelet which appears like it should be connected to the positive terminal
2) A big multi-pin socket which has a clear connection point on the positive terminal but is also unplugged

Hopefully someone with a similar vehicle can provide the answers, or at least a picture of how it should be wired!

 

[rayc]

if you search for 'Fiat Ducato flying lead in battery box' you will get several hits with suggestions such as for tow bar electrics but nothing conclusive. As i say my flying eyelet cable was connected to positive and the socket unconnected.
I personally doubt it has anything to do with tour MIL being on.

https://www.motorhomefacts.com/threads/whats-this-plug-found-in-the-battery-compartment.149530/#lg=thread-149530&slide=0

Ducato mystery loose lead and plug in battery compartment

Anyone know what this is for? It comes in from under the floor to the left of the battery bay and has a plug on the end and also an earth connection. Im not sure if its related but the bench seat of the van was replaced with a captains seat before I bought the van so it may be something to do...

www.motorhomefun.co.uk

 

[oskin]

Thanks rayc, it could well be for unfitted dealer options as you suggest. What's strange about mine, and different to yours, is that I have the female end of the connector already mounted to the battery which might imply that I do have the option it just isn't plugged in?

I'm hesitant to just plug it in but I do wonder what it would do?

 

[rayc]

I have the female end of the connector already mounted to the battery ?

Where is that exactly in your photo?
I found this post on the forum. The picture posted by HughJampton shows the socket plugged into the 'battery isolator'. If I remember correctly this was operated by a position on the ignition switch to allow for lay up isolation.

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@Communicator has commented on the topic

 

[oskin]

Yes d

Where is that exactly in your photo?
I found this post on the forum. The picture posted by HughJampton shows the socket plugged into the 'battery isolator'. If I remember correctly this was operated by a position on the ignition switch to allow for lay up isolation.

Ducato x250 - loose cables / plugs | FIAT Ducato

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@Communicator has commented on the topic

Ah yes, it does look similar to that!

Sorry I’ve realised that I’m completely wrong. I thought the black connector on the terminal received the plug but I’m trying to take a picture to show you I’ve proved myself wrong..!

 

[the green vanper]

tow bar electrics

FYI, the factory module for the tow bar is installed in the driver's side step.

Photos here:

Fiat Ducato original factory trailer tow bar wiring harness connectors colours photos diagram help | FIAT Ducato

Hi I I am trying to make the wiring for the original Ducato factory tow bar (made by westfalia), going to the original Ducato tow bar electric control module unit. There is a black 12-pin connector from the original Ducato tow bar electric control module unit located to the right front sear...

www.fiatforum.com

 

[RS3100]

Whatever it's for, it's quite normal, usually tucked down the side of the battery where it can't accidentally make a connection to the positive terminal plate. If you start poking around under seats, behind the dash, in the engine bay and other places, you'll almost certainly find quite a few looses cables with unterminated connectors. The wiring loom is standard, but not every vehicle has all the options that the loom can accommodate. It's the same on many vehicles these days.