Ducato Problem with doors locking and unlocking on their own

[SallyJG]

I have a Fiat Ducato Pilote Motorhome. Yesterday the front passenger door (only front door) kept locking and unlocking even though the engine was not on.
When the engine was started the wipers, headlights and indicators began flashing. It stopped after about 20 seconds, but kept doing it again until the engine was warmed up. No problems again until 2am when the door problem started again. It kept happening until around 6am then it stopped, but as I am writing this it has started again. I disconnected the negative terminal from the battery but it is still happening.
The battery was new at the end of October and the engine starts first time.
The engine battery shows between 13.3 and 13.7 on the instrument panel. There are 2 leisure batteries and they are showing full.
The local garage brought a meter to the van and said it was probably the alternator as the problems kicked in when the battery fell to12.5amps.
Is that likely to be the problem or something else?

 

[Anthony489]

Hi Sally

Bear in mind that on a motorhome like yours some of the electrics will be Fiat supplied, for which details are well documented, and the rest will be supplied by the converter (Pilote) which are more of an unknown.

I'm finding it a bit difficult to diagnose from your description. Do you mean that items like indicators kept flashing even with the vehicle (engine) battery negative disconnected ? Or do you mean that you disconnected it for a period, reconnected and the odd behaviour was still there ?

Both engine and habitation (leisure) batteries should show about 12.5 volts when fully charged but resting (i.e. not actually being charged at the time of measurement) and about 13.5 to 14.5 volts when being charged from the engine or an on-board battery charger from mains hookup.

When you get multiple items behaving oddly at the same time, there is usually a common cause. By that I mean that all the items share a single piece of wire, fuse etc. This can be in the "live" 12 volt feed, or an earth return to the body or engine block. Earth returns are more prone to corrosion and bad/loose contacts so I would check those out first. Sometimes dismantling and cleaning is required even if they look OK from the outside. If the van starts OK that suggests that at least the live feed to the starter and its earth return are OK.

The only other thing I can think of is that circuits in the vehicle which are supposed to be off are somehow getting "back fed" from the habitation battery when they shouldn't be, for example due to two wires shorting together. Is the habitation control panel behaving itself ?

Your local garage sound like they are guessing a bit. If you don't find an obvious cause I'd suggest going to someone more familiar with the particular issues of motorhome electrics.

 

[SallyJG]

Hi Sally

Bear in mind that on a motorhome like yours some of the electrics will be Fiat supplied, for which details are well documented, and the rest will be supplied by the converter (Pilote) which are more of an unknown.

I'm finding it a bit difficult to diagnose from your description. Do you mean that items like indicators kept flashing even with the vehicle (engine) battery negative disconnected ? Or do you mean that you disconnected it for a period, reconnected and the odd behaviour was still there ?

Both engine and habitation (leisure) batteries should show about 12.5 volts when fully charged but resting (i.e. not actually being charged at the time of measurement) and about 13.5 to 14.5 volts when being charged from the engine or an on-board battery charger from mains hookup.

When you get multiple items behaving oddly at the same time, there is usually a common cause. By that I mean that all the items share a single piece of wire, fuse etc. This can be in the "live" 12 volt feed, or an earth return to the body or engine block. Earth returns are more prone to corrosion and bad/loose contacts so I would check those out first. Sometimes dismantling and cleaning is required even if they look OK from the outside. If the van starts OK that suggests that at least the live feed to the starter and its earth return are OK.

The only other thing I can think of is that circuits in the vehicle which are supposed to be off are somehow getting "back fed" from the habitation battery when they shouldn't be, for example due to two wires shorting together. Is the habitation control panel behaving itself ?

Your local garage sound like they are guessing a bit. If you don't find an obvious cause I'd suggest going to someone more familiar with the particular issues of motorhome electrics.

Hi Anthony
Many thanks for replying so quickly.
It is just the locking and unlocking that happens when the engine battery is disconnected.
When I turn off the 12v supply to the van it still happens.

 

[Anthony489]

Hi again

If the locks are still making noises they must be getting 12 volt power from somewhere !

Your habitation door will have electrical connections to it, which have to bridge the hinge.

This may be be a set of visible metal contacts which mate together only when the door is closed. Such contacts may respond to cleaning, or adjustment if they are not quite touching properly.

Alternatively, the maker may have used a flexible wire loom, usually covered in a tubular rubber protector. Such looms have to put up with continually being flexed back and forth, which can eventually result in one or more wires breaking inside.

What model/year is your van ?

 

[SallyJG]

2010 model.
It is the passenger front door, not the habitation door.
Of course when I disconnected the battery and turned off the 12v supply, there was still a problem - the 240 lead was plugged in!! When this was removed, the problem went away.
Does this change what you are diagnosing as my problem?

 

[Anthony489]

Hi again

If your 240 volt mains is still connected, the onboard battery charger may well continue to supply a charging voltage of about 13.5 volts even if you don't have a battery fitted/connected. This will be enough to carry on powering up the van electrics.

I'm still of the opinion that a faulty earth connection somewhere is the most likely cause of your troubles, but as I'm sure you will appreciate, it's hard to do a diagnosis from behind a keyboard miles away !

I suggest you try posing your question on the motorhomefun forum, where there may be folks more familiar with motorhome electrics.

I also note that there is a company very near you at Goring-by-Sea called "Motorhome Workshop" , but I have no personal experience of their work.

 

[SallyJG]

Thank you so much Anthony for your help. Greatly appreciated.

 

[Crossingkeeper]

An interesting problem but I agree with Anthony that is it difficult to diagnose without being 'hands-on', however I can suggest an explanation for the 'back-feeding' of the cab electrical system as mentioned above based on my own van (2010 Autotrail)

This has an unsophisticated PSU so charging of vehicle or habitation batteries from EHU has to be manually selected on the control panel. To overcome this I have fitted a B2B unit which connects the van battery to the charging input (Solar or EHU) whenever the habitation battery voltage rises above a preset level.

If this is also the case for Sally's van, with EHU connected and the PSU switched on, the cab electrical systems could be powered up even with the van battery disconnected.

Sorry I can't help with the diagnosis of the underlying fault!

 

[SallyJG]

An interesting problem but I agree with Anthony that is it difficult to diagnose without being 'hands-on', however I can suggest an explanation for the 'back-feeding' of the cab electrical system as mentioned above based on my own van (2010 Autotrail)

This has an unsophisticated PSU so charging of vehicle or habitation batteries from EHU has to be manually selected on the control panel. To overcome this I have fitted a B2B unit which connects the van battery to the charging input (Solar or EHU) whenever the habitation battery voltage rises above a preset level.

If this is also the case for Sally's van, with EHU connected and the PSU switched on, the cab electrical systems could be powered up even with the van battery disconnected.

Sorry I can't help with the diagnosis of the underlying fault!

Thank you Crossingkeeper for your clear explanation.