Overcharging alternator - 130i

[Dingdangdutt]

Not quite the introduction post I wanted to do, I collected my 130i last week and the same day after a decent drive home encountered some issues with rough idle and a strange almost supercharger like whine under revs. Immediately shut the car down. Crept to my local indie the next day who then proceeded to shut down for Easter!!!

Turns out my alternator is on the blink and is overcharging, causing the rough running and the whine being the alternator clutch pulley.

Has anybody else has similar issues? Searched the forums and it doesn't return much. Previous owner (was a private sale) has been brilliant and helped where they could informing me it was on its original battery and alternator.

Looking forward to a more positive introduction post soon!

[holland130i]

all n52 engines have the pulley whine...if it becomes to loud you can replace it...doesnt cost much.
if the whine doesnt tone down after replacing it it could be the alternator bearings themself...but you can check that when replacing,or working on the pulley...so best to figure out which one,or both need replacing!

overcharging??.... to be honest never really heard about that!



Mark.

[Dingdangdutt]

There are a few posts about it on E90 and mainly in US https://www.e90post.com/forums/showthread.php?t=1496247

[MPN1]

When my battery was on the way out a battery specialist and a tyre garage that did batteries both reckoned my alternator was on the way out and it was overcharging.
It wasn't.
Replaced the battery, had it coded, and all was well again.
How old is your battery? Might be worth fitting a new one anyway.

[Dingdangdutt]

Battery is the original I believe, so is getting on but I did ask this of the garage and they said it was operating fine once the alternator was replaced. Just out of interest and due to the fact my mileage is likely to be very low, how much is it for a new battery and coding? Thinking it's likely I will need one at some point.

[SteveoE81]

Battery is the original I believe, so is getting on but I did ask this of the garage and they said it was operating fine once the alternator was replaced. Just out of interest and due to the fact my mileage is likely to be very low, how much is it for a new battery and coding? Thinking it's likely I will need one at some point.

Just had mine priced up at a specialist.
You want a 80ah battery. If you go to an Indy they will likely tell you they you want a 70ah and that’s what you will be offered probably if you put your reg in to Halfords or ecp.

Go for the 80ah tho as that’s what the 130i should have.

I actually just had mine priced up at a specialist. Looking at around £180 + VAT for a genuine bmw one.

[Dingdangdutt]

Cheers, good to know. One to factor in the future I imagine.