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Discussion Starter #1
My C-max ((2004Zetec 2.0d) is behaving rather strangely.

The alternator warning light comes on when you switch the ignition on & goes off when the engine is running (i.e. just what it should do) but checking it more thoroughly with a voltmete in the cigar socket, the battery voltage gradually drops over several days and (unlike my other car & every other one I've tested) doesn't shoot up to 14V whilst the alternator is running. I'm thinking ‘alternator relay' but perhaps there are other possibilities (hopefully even a fallen off wire).

Exactly the same thing happened back in November but for no apparent reason it righted itsellf after a couple of days.

I've seen an earlier item here about 'slipper bearings' but the alternator does appear to be turning (& in any case if it was stopped , shouldn't the warning light come on ?). Does anyone have any ideas ?

Eric
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Do you get alternator boltage when the engine is running and does it remain soif you turn on the heavy currnt users (when the engine is at about 2500 - 3000 RPM)

I seem to remember there is a smart regulator so it may not jump straight to 14.5V
 

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Discussion Starter #3
Thanks for your input.
I guess 'boltage' is 'voltage' (why do they put those keys so close together &lt;g&gt;). If so, then I really don't think so. Battery voltage (measured @ cigar socket) drops a lot immediately after starting then recovers a bit but never quite gets back to where it was before engine was started. I think 'voltage recovery' without any contribution from alternator is fairly normal - indeed, voltage actually rises (only 0.01 or 0.02 V) after engine is switched off.


I'm currently charging battery so that next time I run engine it should start from a higher figure & perhaps have a better chance of showing the 14v I'd expect.
The thing that really puzzles me is the warning lamp behaviour. If you believe that then there's nothing wrong - except that after ignoring situation for a couple of days battery voltage has dropped too low to start engine.

Eric
 

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Discussion Starter #5
Thanks. after 2hrs charge I've just taken it for another run. There was a definite hint that voltage was higher with engine racing than ticking over but it definitely dropped as lights were switched on.

When this happened a few weeks ago I was in two minds whether it was alternator or battery but after a couple of days uncertainty (& several overnight charges) the system seemed to right itself and was indeed chucking out 14v when running. It was of course the battery then (other evidence as well) so that's now been replaced (& yes, new one has got a 'silver' label on it).

I'm inclined to suspect the 'smart charge' system too but am not sure what to replace to cure that. I presume there's an alternator relay somewhere in one ofthe fuse boxes but the owners handbook is less than helpful on which of the anonymous black boxes it will be.

Not directly connected to this query but does anyone have a list of which fuse does what ? Handbook claims there should be a list in box but I'm blowed if I can agree that it's any help at all.
 
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