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Discussion Starter · #1 ·
Hi all

About 3wks ago my alarm went off during the early hours. Not even the keyfob worked. So, I disconnected the battery. Later that day I jump started the car, and went out for a drive for about 1hr. Came back and all was well.

Fast forward 3wks... I've been out and about earlier - then I parked the car up. Went back to it about 30m later, opened the door using the keyfob, put the key in the ignition, turned it over, but nothing. Not even a click from the starter relay.

I should add, I changed the battery in January after the cold spell finally killed off the original.

Appreciate any help!
 

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I would do a search for FSU, it's quite likely it could be that. I would be surprised if it were your alternator. If it were the lights would be on the dash when the engine is running indicating it's not charging. Also on the dash you can get to a 'secret' menu and on this the current voltage is shown, this will most likely increase with the car running indicating a healthy alternator.

Alternators in my experience are very robust. I've not seen many cases on any car where the alternator failed. I would do the search on the FSU and go from there.

Cheers

Craig

PS Also the FSU is about £40 (can't remember exactly but in that ballpark), c3bmw online do them, rather than £100's for an alternator! My money is on FSU.
 

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Discussion Starter · #3 ·
Cheers - I had a look through previous posts re: FSU, but Im not so sure its that as I'm not having any issues with the AC / Fan. I guess it's hard to diagnose without an ammeter. It's time for a service, so I guess I'll get CPC to check it out.
 

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Shortly after I purchased my M, the alternator went and in a rather strange fashion. The "battery" warning light on the dash would illuminate but only upon heavy acceleration and the secret menu battery test yielded low-but-still-normal readings. Eventually after doing a lot of research and testing, I decided to replace the alternator. It was rather easy, and I didn't need to even remove the fan (went in from the bottom, unbolted the PS pump, and bingo).

If your confident with a spanner, and can find one for a good price, I would see no hesitation in replacing a questionable alt.

How many miles are on your car ukwill?
 

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FWIW, although there is some great advice there regarding the alternator, as you can see the lights on the dash illuminated (even if it was for a short time). This is a prime indication of an issue. As for the FSU, I will give you my account. I had similar problems, my fans behaved perfectly normally during car operations. I would never have noticed a problem you would assume my car was fine. Car battery dying all the time, going flat overnight, going flat during the day and so on. I tried numerous things and nothing. I replaced the FSU (found it was the old type) and it's been good as gold since.

I believe and from my experience, the FSU is your strongest candidate here. Change it before changing your alternator! Alternators are expensive but as previously said, are relatively easy to swap. You're in surrey, I am in Hampshire, if you wanted I'd help you swap it if it comes to that, but I am pretty certain it will be the FSU.
 

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Discussion Starter · #7 ·
Is there a way I can bypass the FSU to test if the battery still fails with it not in use? (if there is, can I leave it unconnected for a period of time without concern - just that it hasn't appeared to die on cue thus far, so I'd like to give it a long enough period of time to test). I'm happy to swap it out, but before I do, I'd like to know it was the FSU at fault!

Thanks for your help!
 

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I think you can simply pull out the the FSU and drive the car around with it removed. It will most likely mean you'll have fan issues with it removed but it should give you a good indication. If when you remove it, it's one of the older FSU models, with the thicker silver prongs on it then I would be even more confident that's your problem.

Take a look at this

http://www.bimmerfest.com/forums/attachment.php?attachmentid=173713&stc=1&d=1233565821

Hope that helps

Craig
 

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Do you get dash lights and the ability to use any electrical accessories at all? Reason I ask is to see if the battery is actually dead. I had battery issues, but also an issue with the starter motor. Jumping it from a colleagues car in work's car park (ill-advised, I know, but I had to get home somehow) resulted in dash lights but still nothing from the starter, it didn't seem to be battery that was the problem. At all. Turns out it was corroded connections on the starter motor, which low on the engine and isn't too well covered by the underbody protection panels.

Once the connections were cleaned up and I got a new battery (depsite the AA telling me twicw the battery was fine), all has been fine since.

So if it 'seems' as though the battery is OK, but still no turning, check the starter motor connections for this Winters crud. Might save on new parts if it's a bit of a DIY... :)
 
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