Charging problem

[Josse]

Hi I have a 1999 2.8 Fiat Ducato DTi Rapido motorhome. I thought the alternator had developed a fault because it was not charging. I have a little volt meter that is plugged into the cigarette lighter socket and it just showed 12volts with engine running. I checked directly at the battery terminals with a quality meter

and it agreed exactly with the cheapo meter. I took the alternator to a specialist automotive repairer and they tested it and said the alternator was fine. I fitted two new terminals to the alternator cables just in case, but there was no sign of a break in the cables. The only thing I have done is to replace all the the terminals to the rear lamps. Also I unscrewed the quick release earth terminal with the engine running but realized my error immediately and reconnected within two seconds. I do not have a owners hand book or any info at all on this vehicle I have checked all the fuses and they are all OK.

 

Any help greatly appreaciated

[Tracker]

You may wish to clarify which battery is not charging? Engine, habitation or both?

 

Sounds like a fuse, relay, bad earth or dirty high resistance connection issue to me?

 

If it's a bad connection it may well be getting hot as it struggles to pass the current and this might be your easiest way if you can trace the wiring to the battery(ies) and locate or dismiss that possibility?

[Alanb]

As Tracker has already stated it would be helpful if you confirmed which battery you talking about.

 

However you mention testing at the cigarette lighter which will be connected to the engine battery, and then say that you got the same 12V reading across which battery? If you are only reading 12V across the starter battery you have a problem, as a charged battery should read about 12.6V after standing for a few hours.

 

Does the vehicle struggle to start ? (With only 12V you could be just running the battery down.)

 

Check that the charge warning light (red) illuminates when the ignition is first switched on.

 

This light is an essential component for the alternator field circuit when starting the engine, and if it is faulty the alternator will struggle to build up its voltage unless you rev the engine hard, and perhaps not even then.

 

The maximum output voltage of the alternator is about 14V, but you will not see this if the batteries are flat.

 

If you only have 12V across the starter battery, with the engine running, the starter battery may eventually fail to start the engine.

 

Try checking your voltmeter on another vehicle that is charging correctly. This will at least confirm that your meter is reading correctly.

 

 

 

[aandncaravan]

We agree with Tracker, sounds like a bad connection.

Suggest you start by replacing the Earth strap, as more than half the low Starter battery charging voltages we see are down to Earth/poor connection issues.

 

 

 

[Alanb]

Multiple post edited out.

[Alanb]

You now have two possibilities to consider. The majority suggestion of a bad connection (including the earth connections), and my suggestion of a possible faulty bulb in the instrument panel.

 

The bulb is easily checked by turning on the ignition. The bulb should light up, and go out when the engine is started and the alternator is generating.

 

If that is OK, may I suggest checking the earthing. A useful check would be to carefully check between the battery negative and the engine. Either of the engine lifting lugs would be a good negative point for your meter. There should be a minimal reading with this test, if the earthing is faulty you could see as much as 2 (two) volts when the engine rpm is raised. (Assuming that you have 12V across the battery.)

 

I have examined my early 2006 X244 2.8JTD. The battery negative cable runs down past the battery tray and under the radiator to terminate on the bell housing near the starter. The alternator is earthed by virtue of being bolted to the engine. With this method of connection, the engine earth strap is not part of the charging circuit for the starter battery. There should however be an earth strap to the chassis to provide a return path for loads other than the starter motor. This includes habitation battery charging.

 

To complete the details of the charging circuit, the alternator B+ connecting cable runs directly to a 125A (pink) midi fuse (Fiat F72, alternator fuse) mounted at the positive pole of the battery. Is this fuse OK? DISCONNECT THE BATTERY NEGATIVE BEFORE WORKING IN THIS AREA.