Need someone to confirm my self diagnosis on my 2002 BMW 330i.

Symptoms
Driving on highway - battery light comes on for 30 seconds and then goes off.
2-3 minutes later - comes on again for 30 seconds and then goes off.

No lights again for another 20 minutes of the drive.
Park car for a while. And then on the last leg of my trip, **** hits the fan...
Speakers shut off (radio unit on but no sound other than crackling) and DSC, ABS and Brake lights come on. Car still drives fine.
5-10 minutes later... radio display starts flickering. ALL the warning lights come on and the headlights go dim.
Turn off lights and cannot turn them back on. (Note all this happened in ~30 seconds)

Pull over onto the shoulder and towed it home.

My diagnosis
1. Battery light indicates that alternator is on its way out.
2. Since alternator wasnt powering - all modules were being run off the battery directly. This emptied the battery and is it was being emptied - each system started shutting off (starting with radio - ending with lights)

Next steps
1. Get a volt meter and one of these: http://www.harborfreight.com/automat...ger-42292.html
2. Test the battery votage - will be low I'm sure - charge it using jump starting or float charger. Then see if car will start up - see voltage at battery while car off (should be 12) and see voltage while engine at 2k rpms (should be 13-14v). If its not 13-14 when car is on - replace alternator.

Questions
1. If battery is fully dead, should I charge it with another car (faster) or while using a float charger linked above.
2. Should I just replace the alternator or is there a way I can figure out if its the voltage regulator thats bad?
3. When I tried to turn the car on/off when radio went off, it just made a loud crackling sound - I hope I didn't blow something? I hope that if the alternator was dying - there would be low voltage, not high voltage - so I SHOULD be ok, right?

 

My old BMW would go through batteries every year and a half and the dealer never found any other problems (because they sucked and were staffed by retards). The batteries would fail almost catastrophically with an internal short to the point that the car wouldn't run (after a jump) at idle. It required a 3 pedal dance to keep the juice flowing at every stoplight on the way home or else that POS would stall. BUT my car was a 1994 5 series, a much simpler car than yours, but if I were you, I would still slow charge the battery the LOAD TEST IT. Some auto parts store do this for free. There is are you have more than one problem going on here, I'd check all the leads and grounds and easy stuff like that too. I've heard of bad alternater taking out good batteries and in the good old days, a simple diode in an alternater would fail and drain the battery at low RPMs.

Wait until you get stable voltage before worrying about the radio, my guess is that it is OK.

 

Alternator regulator... find out which one alternator you have whether it be Bosch or Valeo and just buy another one because you cannot replace the regulators on this model alternator without doing an overhaul. Check the amps in the alternator as well. My 330i had this problem and it was fixed with a new alternator


happy motoring.

 

Battery with engine off reads at 11.4 volts.
With engine idling reads at 10.3 volts. And same at 2-3k rpms

Left the trickle charger on it for now while I figure out what above means (solely because I bought a trickle charger lol)

Anyway, does voltage drop when engine on confirm bad alternator?
How can I check if it's voltage regulator or some other part of the alternator? I believe I read somewhere that its a visible difference but not sure...