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Hello all,

I have an E46 330 Sport Conv Auto on a 52 plate. I have had the car for a year now with no problems. I had the car MOT'd last week and was advised that the brake pads needed changing so I had the front ones replaced. A couple of days after this the starter motor seized so I had a new one fitted, since then I have this problem.

The battery light was coming on for the first 10 seconds of every drive but then going out and everything was ok. This morning however the battery light stayed on for my entire journey. After so many miles a few more lights came on, one being the ABS light, at this time the car became stuck in what I presume is 3rd gear. There was a little exclamation mark next to the D for drive on the dash. I tried to put it into tiptronic and change the gear but it wouldn't.

I drove to a garage and turned off the ignition, they came out to test my alternator and the car started fine with no dash lights on, the volt meter read between 12.8 and 13.2 volts. I decided to drive the car round to a BMW specialist around the corner but the car drove perfectly, no dash lights and the gearbox was working.

I decided to come home and do a bit of research, the car drove fine all the way home and the battery light occasionally flickered on. My car seems to start everytime which leads me to believe that the alternator is ok, on the way home I had my headlights and heaters on but it drove fine.

Sorry it's a lot but, any suggestions?
 

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Thanks for the answers. I just checked the battery using the hidden function on the instrument panel, when the ignition is off the battery gives 11.7 volts, when I started the car it first went to 13 volts. I then turned on the headlights, heated seats, air con and radio and it rapidly dropped to 11 volts. I'm guessing that the alternator is fubar.
 

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Not necessarily - it may just be the battery isn't holding - about £100 to find out vs several hundred for a new alternator!!
 

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Not necessarily - it may just be the battery isn't holding - about £100 to find out vs several hundred for a new alternator!!
Regardless of if the battery is holding charge or not, when running, the alternator should be supplying circa 14volts to the electrical system - if the electrical circuit tests under this on load, then its clear where the failure mode is. Alternator change is an easy DIY change on the 330's
 

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Thanks for the answers. I just checked the battery using the hidden function on the instrument panel, when the ignition is off the battery gives 11.7 volts, when I started the car it first went to 13 volts. I then turned on the headlights, heated seats, air con and radio and it rapidly dropped to 11 volts. I'm guessing that the alternator is fubar.
what hidden function:confused
 

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Actually get hold of a Fluke / reliable multi-meter, and take a reading across the battery terminals with the ignition OFF, then with the car running.

When the car is running, get someone to give it a rev half way up the tach. Do this a few times, and you should see the charge increase to around 14 volts (14.4 in an ideal world).

Do this same test again, with all the electrics on you can switch on - radio, air-con, all lights on, with headlights on high beam etc etc. If the battery is reading anything lower than 12 volts when revved (again, to about halfway) chances are, your alternator has expired.

BUT, a dead battery can also cause this.

If you have a mate with a battery that fits your motor, borrow it, and see if the same readings and symptoms happen. If they do, you know more or less it's the alternator. If not, then you are lucky, and only require a battery.



What I will say though, is when your friend revs your motor, get him to hold the revs steady for a few seconds with the tach needle at the 12 o'clock position, to get a good reading, and to allow the Fluke to 'catch up'.
 

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Discussion Starter #10
UPDATE: Turns out the mechanic who fitted the new starter motor didn't attach the wire that led from the alternator. After messing about with a new altternator the mechanic inspected the starter motor, realised this and everything has since been fine.
 

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Always assume the spanner monkey was to blame first, esp if everything was fine to begin with! Don't go back there, might be the brake pads next time!
 
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