Battery disconnected - cab interior light comes on (1 Viewer)

[StuAFCB]

Hi all..
I have had what appears to be a very common problem with the airbag ECU on my 2016 Ducato based MH.. With thanks to threads on here and various YouTube videos, I've got that out and am awaiting its return from Crash Data.. but having disconnected the negative terminal on my starter battery to remove it I noticed that the interior/door lights in the cab were still coming on. That err.. confused me!

Is it possible that the cab lights are running from the leisure battery? I have a battery master fitted and a solar panel on the van if any of that would make any difference.. I'm concerned that there might be a wider problem with the electrics that may have caused the ECU problem in the first place..

Thank you for any help!
Stu

 

[PeterCarole29]

Hi all..
I have had what appears to be a very common problem with the airbag ECU on my 2016 Ducato based MH.. With thanks to threads on here and various YouTube videos, I've got that out and am awaiting its return from Crash Data.. but having disconnected the negative terminal on my starter battery to remove it I noticed that the interior/door lights in the cab were still coming on. That err.. confused me!

Is it possible that the cab lights are running from the leisure battery? I have a battery master fitted and a solar panel on the van if any of that would make any difference.. I'm concerned that there might be a wider problem with the electrics that may have caused the ECU problem in the first place..

Thank you for any help!
Stu

hi i would assume you battery master is doing what it should and feeding the terminals of the engine battery

 

[PeterCarole29]

i would take out the battery master fuse

^{_{Subscribers  do not see these advertisements}}

 

[leann53]

Try moving interior light switch to a different position and see if that work,s

 

[StuAFCB]

i would take out the battery master fuse

I've just popped out to the van and tried - but the lights still come on..

I'm (probably obviously) no electrician... but having read that I need to reinstall the ECU with the battery disconnected, what I don't want to do is reconnect it if there's a current that might immediately break it again..

 

[StuAFCB]

Try moving interior light switch to a different position and see if that work,s

Both the lights work as normal in all positions..

^{_{Subscribers  do not see these advertisements}}

 

[Bobby-gg]

Have you got a multimeter?

Check to see if you still have voltage on the vans battery terminals - if you have, you've still got a feed from the leisure battery

 

[denisejoe]

Just disconnect the habitation battery

 

[jezport]

Does your solar also go to the leisure battery?

^{_{Subscribers  do not see these advertisements}}

 

[StuAFCB]

Does your solar also go to the leisure battery?

Yes, the solar feeds the leisure battery which then tops up the starter battery via the battery master..

 

[IRHP]

Have you got a multimeter?

Check to see if you still have voltage on the vans battery terminals - if you have, you've still got a feed from the leisure battery

Don't you mean the battery cables?

 

[pappajohn]

Just disconnect the hab battery.
If the light goes out then obviously the battery fed the light.
If it stays on the solar panel is still live.
Disconnect the panel at the solar regulator.

^{_{Subscribers  do not see these advertisements}}

 

[StuAFCB]

Have you got a multimeter?

Check to see if you still have voltage on the vans battery terminals - if you have, you've still got a feed from the leisure battery

Yes.. tested putting probes on each of the terminals (not posts - positive is connected to the post still, negative is disconnected) with it set up the same as I have it for checking the charge (DC voltage, 20 range) and there is voltage measured - reading fluctuates a bit..

 

[Ray-Vic]

If you have only disconnected the negative cable from the cab battery and have a battery master installed, it will probably still be picking up a negative via the chassis to the leisure battery. You will need to drop off both negatives (leisure as well) and then try again.

 

[StuAFCB]

Just disconnect the hab battery.
If the light goes out then obviously the battery fed the light.
If it stays on the solar panel is still live.
Disconnect the panel at the solar regulator.

The van has two leisure batteries - one under the driver's seat and one under the sofa.. the battery master is connected to the one under the sofa - I assume I would I need to disconnect both but would the sequence matter?

^{_{Subscribers  do not see these advertisements}}

 

[Ray-Vic]

Deleted.

 

[gus-lopez]

The van has two leisure batteries - one under the driver's seat and one under the sofa.. the battery master is connected to the one under the sofa - I assume I would I need to disconnect both but would the sequence matter?

No.

To isolate completely you need to disconnect the van battery , both terminals, same on all lesiure batteries. Then remove fuses or disconnect both cables from the solar panels to controller as otherwise there will be a feed still.

 

[StuAFCB]

I guess before I go to these lengths, the question I should be asking is if I am right to be worrying about reconnecting the ECU?

^{_{Subscribers  do not see these advertisements}}

 

[StuAFCB]

Disconnecting the battery master both positive and negative cables (with positive and negative marked tape) seems to have done the trick. There's now no voltage across the starter battery terminals, the lights don't come on and I feel comfortable to reinstall my airbag ECU. Just giving the starter battery a bit of a charge to make sure it's completely full before I do..

Thank you everyone for your help and suggestions. I've got another stupid question to ask shortly but one thing at a time!
Stu

 

[PeterCarole29]

Im not sure but i thought i read somewhere there is a set proceedure for reconecting after doing an air bag worth doing a search or someone who does know will say hopefully

 

[StuAFCB]

Im not sure but i thought i read somewhere there is a set proceedure for reconecting after doing an air bag worth doing a search or someone who does know will say hopefully

I found a procedure for battery removal - https://www.motorhomefun.co.uk/foru...y-top-up-or-removal-replacement-for-x290.370/ - not specific to the airbag ECU but referenced in that context.. I'd done everything it says more by luck/paranoia than judgement (other than opening the driver's window) but I will make a copy of those steps, add in the disconnection of the battery master and print them out to keep in the van for future reference. Might laminate them and stick them on the underside of the panel that covers the battery compartment...

^{_{Subscribers  do not see these advertisements}}

 

[LithiumConvert]

There's now no voltage across the starter battery terminals, the lights don't come on and I feel comfortable to reinstall my airbag ECU

If you have not already reinstalled the Airbag ECU, then remember to leave the vehicle alone for an hour after disconnecting the engine battery - and then you can reinstall the aiibag ECU.