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gizmo

BMW 330i Sports - Battery light on and eventually, no power

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Hi

Got a BMW 330i Sports (Auto), year 2000.

It's been fine until today when the red car battery light appeared on the dashboard even after the engine was running. Got about 8 miles and then it started to lose power and stopped...luckily only 400 yards from home! So I managed to push it home, just.

Electric metre shows between 9-10 volts when its off. I gather a battery should be between 12-13 volts. About two hours later, I turned the key and it started again, and while it was running, the battery showed 10 volts, but it soon died again. And again, when off, 9 volts. So my assumption is the battery is faulty, but I only bought it about a year ago. Granted, it was not a top end battery, so maybe it's just not up to running such a powerful car. But I'm also wondering if its the alternator, which is much more expensive.

What do people think?

Edited by gizmo

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Could be alternator or starter motor on the way out, my battery light came on and I couldn't get the bugger started after I switched off, which leads me more to the alternator, get a mobile electrician to check mate it's the best way

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10v suggests a dodgy alternator. People like Halfords will do a free battery test, if you're able to get it there (maybe just the battery will do?)

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How olds the battery? I replace mine every 2 years, I'd get the alternator checked just incase mate, could be a underlying problem which you can fix now rather than wait for it to develop into something worse and the car cut out when your not as close to home

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Alternator for sure.

Replacing batteries every 2 years? that must get expensive and is really unessary. Buy a quality battery and it will last for years.

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It's 17 months old (the battery) which I know is not that old, but given it was the cheapest line they had that was powerful enough for that car, maybe that is the problem (I say hopefully!!). It was only a local car parts shop as well - not a major branded place like GSF Car Parts or Euro Car Parts. And the battery isn't particularly branded either (Lion, I think), so it's not a BOSCH or anything. It cost me about £70 if I remember rightly. Looking at ECP and GSF, batteries for that car range between £110 - £250.

If it is the battery (and yes, I'll take it to a garage to have it tested before replacing it), can anyone recommend a particular battery for the car that are know to be good and reliable? Or doesn't it actually make much difference?  There's this BOSCH one : would that be suggested? http://www.eurocarparts.com/ecp/c/BMW_3+Series_3.0_2000/p/car-parts/electrical/car-electrics-and-car-lighting/car-battery/?444771107&1&414bc9c661da3f57201caff37811a37754a9403e&000020

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I fitted a Yusa battery to mine, was slightly over spec for the car. £170 with discount but garuanteed to last. 

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40 minutes ago, R11CH said:

Alternator for sure.

When you say "for sure", how do you know? I only ask to save me time and money...not challenging you.

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9 hours ago, gizmo said:

When you say "for sure", how do you know? I only ask to save me time and money...not challenging you.

Because its the same symptoms when mine went. 

I jumped in the car drove off then less than a mile down the road the battery light came on, drove another few miles and the light was on and off before it stayed on permanently, the car was down on power.

To test it i turned everything electrical  on which threw the battery light on and then i started getting other lights come on the dash as the battery was dieing it could no longer keep power to run vital parts.

A dead battery would fail to start the car in the first place or would be very slow to turn over.

You can access the battery voltage part in the hidden features on the cluster to see what its doing both with engine off and running.

Hth

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Will be alternator if it cut out whilst running and wouldn't start.

The car would run off the power generated by the alternator once started, even if the battery wasn't holding charge.

Not saying your battery isn't knackered as well as that's likely the case now too.

Edited by bennno2005

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I took battery to garage and they said it fine. Told them symptoms...they agreed with you guys. Likely alternator.

So, I have spent some time removing the alternator with some success which makes a change! I need to get the correct replacemement for it. The one out the car has the following details on the label :

BMW 7 501 593 VALEO

70/120A

14V

029971  S42AN00

SG12B029

Which I think this will match from EuroCarParts. The only think confusing me is that ECP list 3 alternators for my car. The one linked to, and this one. (and a third thats £500 so no point looking at that!). One says 80 amps, the other says 120 amps. The label on my existing one says 70/120A...so does it matter which I get? 

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I've got a spare alternator for mine kicking around (I thought it was faulty, but now it seems it was a combination of two other faults making it seem that way). When I was looking, people weren't too complimentary of those cheaper brands, and I think RTX was generally an 'avoid' make. I got a new BOSCH one for ~£235, which I think it worth the extra, personally (although as it's never been fitted, it was a complete waste!)

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Well I got a new alternator and replaced the old one. Engine now seems run :-) No warnings lights on dash, and car seems to have plenty of power etc.

But there's a problem...the new alternator is unusually loud. I tried putting the old belt back on instead of the new one in case the new one was too tight, but no difference. For anyone who has the time to download the 159Mb video I recorded of it, I'd appreciate your views as to whether this sounds normal for a reconditioned alternator, or if I should send it back?

https://my.pcloud.com/publink/show?code=XZhvmbZIQmkf7KBuIkwhIlrz2aqfj5z2LR7

Also, the retailer who sold the alternator have asked me to "check the alternator tensioner". COrrect me if I'm missing something, but aren't they self tensioning? So if I just assembled the alternator in the reverse steps as I took it out, I shouldn't need to check\change\adjust any of the tensioners should I?

Thanks

Edited by gizmo

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