02' 540 Alternator dying?

The charge light came on while driving yesterday. Went to the local auto parts store and had them check the battery and voltage output from the alternator. Battery is fine (for now) but am getting barely 12 volts at 1500
rpm from the alternator. Don't know what the spec is but assume it should be around 14v. Before I take the water-cooled beast off the car does anyone have any advise on what else I need to check?
Thank you, Mark
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The advice you have been given is correct - dead alternator - however as you appear to be vague on the basics of motor vehicle repairs I suggest you get a recon one fitted.
Anybody else I would say it either the diode pack or the regulator gone down but it could also be a broken winding in one of the coil packs (rare) and if you have no idea of what I'm talking about the go back to my first bit of advice.
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Sir Hugh of Bognor

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I take it you've not heard of water cooled alternators? ;-)
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*A day without sunshine is like... night.*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Dave? What's water-cooling got to do with no electrical output?
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Vague? That's a bit presumptuous Sir Hugh of Bognor. Thanks for the advise though. In the future when handing out advice on alternators you might suggest that they take it to a Starter/Generator shop if one is available. It cost me $50 to have one rebuilt on my '90 535 and it lasted 125k miles before the tree smashed it. Hope this one comes in under the $400 for a reman. Thank you again, Mark Oh, and you are correct...Intelligence is not knowing the answer but knowing where and how to find it! :-o
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Mark
If you already knew the answer - why ask the question? You could have asked for confirmation of the diagnosis - which was not given.
You simply said - basically - 12V at the battery so the alternator is not giving an output. Yes! I presumed you were vague on the mechanics as there wasn't much in depth technical information that one would have expected from a knowledgeable person.
What else to check before you remove the offending item - ! make sure you have the possibility that new hoses and clips might be required, the correct size spanners and screwdrivers, the possibility that you may have to replace the coolant or at least top it up, disconnect the battery, refer to the hand book regarding the battery disconnection....
What else is there?
If I felt, by your question, that you wanted to know how to rebuild the alternator then I could give you chapter and verse but that was not the case as you said - fit a rebuilt unit.
Strange though I have never had an alternator die on any BMW I have had and my old E38 740i had the original after 13 years and 190K miles. I did have an "Autolite" (FORD) alternator die on my UK Mk1 Granada in 1976 after 40K.
Anothr thing is that in my 30 years in the motor trade (ended in 85) I never had any cause to replace a coil due to it failing but a friend that owned a parts store said that auto coils were one of his fastest movers and profit lines.
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If this is the original battery, I'd suggest the battery is toast, and is dragging the alternator down.
You need to have the battery checked by somebody that actually knows charging systems. A shorted cell in an old battery can easily cause poor charging.
You're right though, the alternator ought to be churning out something like 13.6 volts.

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