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-   -   Bad Alrernator 00 BMW 740il (http://www.bimmerfest.com/forums/showthread.php?t=663018)

Alex7 12-08-2012 10:53 PM

Bad Alrernator 00 BMW 740il
 
Hey you guys, i'm kind of new at this so let me try to make this as simple as possible. I drive a 2000 BMW 740il and I'm now developing a problem I think with the ALTERNATOR, when it's running it sounds great but when I turn on my lights the whole car dies so if you guys could, can anyone please tell me if this sound like the ALTERNATOR-Thank You:)

JasonSC540ia 12-11-2012 03:48 AM

When the Alt go's bad 85% of the time you will get the red battery light on the dash. Not always the case. It is possiable for the ALt to produce volts but no amps. That sounds like whats going on in your situation. The only way to really tell would be go to a shop where they can do a load check to see if your alt is producing amps.

bluebee 12-11-2012 09:04 AM

As stated above, you often get the red battery light way too late (ask me how I know).

But you're in good company as almost everyone has had to replace their battery and/or alternator at least once by now.

These links are for the E39 but they should apply as well to the E38:
- DIY how to test a BMW battery & alternator

If you have to replace the battery, I think you use the same one we do - if so - these should help:
- What batteries to purchase (1) and a simple battery replacement DIY (1)

if it's the alternator, these should help:
- How to test your generator (1) & how to determine exactly what alternator you have (1) & a DIY for replacing the V8 alternator (1) (2) (3) (4) & why rebuilding an alternator is preferable to replacing (1) & cdawg246's quest for materials for a Bosch water cooled alternator rebuild (1)

Alex7 12-12-2012 07:36 PM

Thanks
 
Thanks for the advice, I'm going to have it looked at from the dealer, jast hope my pockets are still heavy as I walk out the door.

BMWFatherFigure 12-13-2012 01:27 PM

Let me guess - Service Advsr "Sorry Mr Alex7, new alternator needed. We have one in stock, only your first born male child and a leg."

anthony s 12-19-2012 06:44 PM

charge
 
you need to check charge system.

BMWFatherFigure 12-19-2012 08:36 PM

Any good auto electric shop should be able to rebuild a BOSCH alternator and give a warranty.

joyism5 12-20-2012 05:40 AM

Quote:

Originally Posted by BMWFatherFigure (Post 7261092)
Any good auto electric shop should be able to rebuild a BOSCH alternator and give a warranty.

Mate, here in US they are not licensed to rebuild the liquid cooled alternator. And rebuild kits are not available for this reason. There are just a few companies that are able to do that...
Once the voltage regulator goes bad, the whole circuit board has to be replaced. My personal search lead me to NAPA autoparts for the best deal: around $300 for the rebuild one.

BMWFatherFigure 12-20-2012 09:17 AM

The problems with intercontinental forums. Our BM's don't have half the sensors yours seem to have for weird stuff like poor fuel cap seals etc.

BTW what is so special about it? An alternator is an alternator. I bet someone has found out which other bit fits and is soldering it in for his mates and saving everyone a fortune. I was told that out here the 'cooling' is actually auto trans fluid that heats up the gearbox from cold quicker. Maybe yours run engine coolant?

joyism5 12-20-2012 01:40 PM

Special about it is that indeed is coolant cooled not air like a regular one. There's no way for it to be cooled by transmission fluid, I think who told you this got confused because the transmission fluid runs through a heat exanger that is connected through a pipe with the alternator. #1 and #2 here http://www.realoem.com/bmw/showparts...62&hg=17&fg=05. When you look at it, yes it gives you the impression that trans fluid will go into alternator, in fact the coolant from alternator comes to the heat exanger to cool/warm trans fluid in the same time with the engine's coolant.
The alternator is big, heavy and sealed, not easy to open.
It is known for worn bearings which can be repaired http://www.meeknet.co.uk/e38/Alterna...eplacement.htm

BMWFatherFigure 12-21-2012 12:02 PM

I've rebuilt alternators B4 but not these ones, I must admit. I did a sealed one on the Eldorado I had but it did not have the fluid connections. I guess I'll have to wait till mine breaks and learn the hard way..

BMW 3-SERIES 01-10-2013 02:44 AM

I replaced my past e38 watercooled alternator. Now I rebuilt them. Replace 2-bears vs paying 350 for rebuilt one

joyism5 01-12-2013 07:29 AM

Quote:

Originally Posted by BMW 3-SERIES (Post 7302820)
I replaced my past e38 watercooled alternator. Now I rebuilt them. Replace 2-bears vs paying 350 for rebuilt one

I'm wondering, how you will rebuild it if, the voltage regulator is bad?

setconstr 01-12-2013 09:30 AM

red
 
It seems that 99% of these articles turn out to be a battery. These cars can develope all types of weird electrical gremlins when the battery starts going even though the battery may test well it turns out that you may only need a battery. Also to me oembimmerparts.com is by far the best company I have dealt with for speed of shipment and price.....

bluebee 01-13-2013 08:38 AM

Quote:

Originally Posted by setconstr (Post 7308220)
These cars can develope all types of weird electrical gremlins when the battery starts going

I agree!
- One user's experience debugging a half-dead instrument cluster (1) which, after testing the fuses (1) battery & alternator (1) thankfully turned into an alternative battery search (1) and a simple battery replacement DIY (1)


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