Ducato 2.8JTD yr 2000, battery light staying on, but it's not an alternator fault (1 Viewer)

[The Nomad]

The background:
Fiat Ducato 2.8JTD Benimar Spanish LHD motorhome, year 2000 built.
It's a coachbuilt motorhome on a bog standard Ducato chassis-cab, so all engine mechanicals/electrical system is bog standard.
Alternator output goes to a charge splitter which feeds both engine battery and rear leisure batteries.

The problem:
Battery light goes out when engine started from cold/after a delay overnight; but has begun to stay on when engine is restarted once warm/after having been run for even only a minute then turned off and restarted.

What's happened thus far:
A mobile "expert" auto mechanic/electrician came over to the house last week, did a few tests with his multimeter and some other kit, and declared the problem to be definitely a dodgy voltage regulator within the alternator.....causing the alternator to not start outputting charge when you started the engine.
According to his kit, there was definitely no output coming from the alternator when engine running and battery light was on.
So, I managed to track down and get an exact matching alternator 2nd hand from a breakers yard.

The chap fitted it and "tested" it this morning, declared problem solved, as when he'd finished I started the engine the battery light went out.
Turned off engine and left it.

An hour later I went to get the MH off the levelling ramps I'd run it up on for the guy to work underneath it. Started engine, light went out, great.
Turned off igniition after maybe 1 minute of ticking over, started it again, and the bloody light stayed on for maybe half a second then went off.
Tried it again and this time light stayed on all the time!
Tried starting it half a dozen times more, and every time light stays on, just as before the alternator swop.

I've got this chap coming back for another look at it in the morning, but I'm not convinced that he's actually quite as expert in vehicle electrics/electronics as he says.
I suspect that all I may actually have achieved with him so far is to get me to hunt all over Spain to buy a second working-fine alternator to swop for the original actually working-fine alternator. So I've managed to get a spare one, if nothing else!



I think what somehow MIGHT have caused this problem to start happening is when I was testing the rear lights after having removed the light clusters to repaint the bar that they sit on. Once replaced, I got my wife to stand behind the van to check each worked.
I started engine and then tested brake lights, reversing light, sidelights, headlights etc.
At the moment that I already had the headlights on and then also pressed the rear foglight button for a moment to test it too, I thought I may have heard a slight click noise from inside the left side of the dash or engine compartment, and I think that was the moment that the battery light first ever came on next to the foglight light on the dashboard. (I cannot even remember the last time I ever previously have pressed the rear foglight switch).
But haven't been able to replicate that condition since.... on the few occasions I've started the van since then from cold and the battery light has stayed off, I've tried then turning headlights on and then foglight once again and all appear to work just fine, and battery light does not illuminate

I've just now disconnected all of the connections from the two rear light clusters and then tried starting the van again, but the battery light still stays on, so I don't think the problem lies there.....at least not now.


I'm now flummoxed.
So, are there any auto-electrician Gods out there who could suggest possible causes/solution for this problem please?

 

[gus-lopez]

You really need to ascertain that the alternator output is good. My local Bosh,Lucas,Magnetti-Marreli shop has a tester that checks battery, alternator condition, output ,etc; so I assume that you could find one where you are ?

 

[pappajohn]

Alternator output goes to a charge splitter which feeds both engine battery and rear leisure batteries.

Is this an electronic gismo which automatically splits the charge or do you mean a regular 12v 30a automotive relay.

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[Xabia]

If you are anywhere near Moraira I can recommend the garage who sorted out my EML problem when Fiat Professional in the U.K. couldn’t.

 

[The Nomad]

If you are anywhere near Moraira I can recommend the garage who sorted out my EML problem when Fiat Professional in the U.K. couldn’t.

Could you give me the garage details just in case .. Many thanks.

 

[TheBig1]

with your first description i suspected the voltage regulator. if you are absolutely certain the new alternator and its regulator is working correctly, i suspect an earth fault

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[pappajohn]

Alternator output goes to a charge splitter

No response to my question but if it is some kind of electronic splitter that would be my first port of call.

 

[The Nomad]

No response to my question but if it is some kind of electronic splitter that would be my first port of call.

Sorry, was offline later on last evening

The charge splitter is a big alloy solid box, maybe 10 inches by 6 inches, with cooling fins, under the mh chassis.
Three terminals on it running down its mid part: basically alternator in, the cable out to engine battery, and out to leisure batteries, and also a thin signal wire which goes to AES fridge to tell it when alternator is running and thus it can use 12volt DC from Leisure batteries as it's power source.

I'm getting suspicious that this may be the issue and today will disconnect cables to it and connect alternator-in cable direct to the lead to engine battery, thus bypassing it, and see if that solves the hit/miss charging when engine is started ...

 

[Xabia]

Could you give me the garage details just in case .. Many thanks.

Here you go:

http://www.autotallerpaichi.com/en/

Easy to find on the road between Moraira and Benitachell (Benitaxell)

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[Barclaybasher]

Don't know if this will help

My 1991 eribacar has had the ignition light on/off randomly for 2 years or more

The alternator charges ok

A mechanic told me it was a 'false' light probably a loose lead just on the light itself and to ignore it - which I have done and crossed France twice with the light on much of the time

 

[chaser]

Don't know if this will help

My 1991 eribacar has had the ignition light on/off randomly for 2 years or more

The alternator charges ok

A mechanic told me it was a 'false' light probably a loose lead just on the light itself and to ignore it - which I have done and crossed France twice with the light on much of the time

thats the thing really , is it still charging even though the light says no, if not , it sounds like an earth connection somewhere that has got conntact when damp , first thing in a morning but then loses conntact as the engine warms up and drys it out. No expert so dont take my word for it but seen similar things many times on older vehicals.

 

[Barclaybasher]

thats the thing really , is it still charging even though the light says no, if not , it sounds like an earth connection somewhere that has got conntact when damp , first thing in a morning but then loses conntact as the engine warms up and drys it out. No expert so dont take my word for it but seen similar things many times on older vehicals.

Charges fine

Light comes on randomly, sometimes on for seconds, sometimes an hour or more, sometimes bright sometimes dim, just got used to it

No problem

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[chaser]

Charges fine

Light comes on randomly, sometimes on for seconds, sometimes an hour or more, sometimes bright sometimes dim, just got used to it

No problem

didnt meen yours mate , you had already said yours was working fine.

 

[pappajohn]

I'm getting suspicious that this may be the issue and today will disconnect cables to it and connect alternator-in cable direct to the lead to engine battery, thus bypassing it, and see if that solves the hit/miss charging when engine is started ...

Certainly worth checking out.
Alternators usually either work or not.
Usual fault in my experience is worn/sticking brushes causing intermittant output.
Regulators/Rectifiers simply fail.

 

[tonyidle]

Whatever happens to the alternator output it will not affect the charge warning light. Normally its circuitry is separate from the charging element of the alternator. If the alternator fails to generate an output for whatever (internal) reason then the charge light circuit, monitoring the output, may remain lit or light intermittently. If the alternator is charging OK (check by monitoring start battery voltage) then the fault is either the charge warning light sensing diodes within the alternator, a connection to the warning light terminal for split charge sensing has a fault on it, or the 12v supply to the back side of the warning light itself is faulty. Either way the first test is to check that the alternator is charging and that the output voltage doesn't change whatever the warning light is doing at the time. If the output voltage is OK whatever the warning light is doing then connect a 5W or less bulb from battery +ve to the alternator warning light terminal (after disconnecting anything else on that terminal). Test next by running the engine to see if your new warning light behaves itself. If it does the alternator is definitely OK.

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[Mike800966]

Simplest way to check if the alternator is working is to switch on the headlights with the engine off, start engine at idle speed and gradually increase revs, you should see a sudden definite increase in headlamp brightness as revs rise. But sometimes the alternator can be charging even at idle revs so you need to check the lights before you start the engine. To be more accurate you would see the same voltage rise effect with a voltmeter across the battery or even cigarette lighter outlet, just be careful stuffing prods into lighter sockets. Do you think that click you heard was a relay operating or was it a fuse blowing?
Mike
Oh ok then G8JXS!

 

[The Nomad]

Update - in case it helps others.

Please bear in mind that I'm not an auto electrician... I've tried to convert the electricians diagnosis and repair technical speak into simple terms!

Turns out it was a faulty inline diode(?) that had been added by the motorhome converter Benimar into the Fiat Ducato standard ignition wiring.

When we removed the split charger from the loop, by connecting the cable out from alternator straight to cable leading to engine battery, vehicle always behaved perfectly...alternator always began charging immediately engine was started and battery light went out immediately.

But the moment those cables were reconnected through the split charger, very often the alternator would fail to wake up and begin charging when engine was started.... hence the dashboard battery light staying on on those occasions.


Apparently turning key to start engine always gives enough "jolt" to alternator on a standard Ducato to always "excite" the alternator so it wakes up and starts generating charge.

But if vehicle converter added a diode based split charger, to send some of the output to a motorhome rear battery as well as engine battery, there isn't enough starter "jolt" to the alternator to wake it up.
Motorhome converters apparently used to get round this by adding a little diode into the ignition to alternator wiring to somehow amplify the wake-up-jolt to the alternator when engine is started.

Electrician solved the problem by removing that wire and inline diode, and replacing it with a beefier wire and a relay.

Now all is fine once again!

The motorhome is a year 2000. I think this old system of a diode based split charger has on more recent motorhomes been replaced with relays anyway, which probably would never give rise to the specific problem that happened on mine.