Doug Butabi

Hello all,

So, every now and again my car will throw me random malfunctions. It's usually a dynamic drive malfunction or active steering, but as most of us have seen, they go away. Twice now, both times many months apart, as I am driving, the car will just completely cut off power, and it will return two seconds later. Once that happens, the iDrive starts going crazy, I get the usual malfunctions, plus a transmission malfunction that will only keep the car in one gear.

Last week, I went to turn my car on, but the brake was oddly stiff, and all the electronics turned on, but when I turned the ignition, absolutely nothing happened. Not a single noise, and not even a single click. I returned the next day and the car started up fine, however on the drive home, the car shut off a couple times for a couple seconds, and I got the usual malfunctions.

I had a mechanic friend come by and in his opinion, I need a new battery, even though the battery should still have two years of life left. He doesn't think it's the alternator because the car has no trouble starting (even though I had the trouble last week). But from what I've read, a shotty alternator can cause the battery to die early. I'd like to think it's the voltage regulator that is making the car act all wild.

So, what say you, 5series.net? I've searched and read through every thread on this topic (of which there are many), but everyone's situation is slightly different and I can't necessarily find my answer in someone else's thread. I will be taking my car in to a BMW boutique this week for them to run a diagnostics test. It's unavoidable at this point.

sanjsanj

unlock secret menu on dash and monitor voltages

Gangplank

How do you do that?

Could be a battery or other power problems. Have you read the codes? Bmwhat app might be helpful.

sanjsanj

sanjsanj

you want menu 9...

gwf545

I had identical problems and did not see odd voltages in the secret menu, they appeared normal. I did see some odd high spike voltages up to 16 using a volt meter connected to the battery. I replaced my alternator to correct the problem. The voltage regulator is integral with the alternator and although some people have been able to replace the regulator alone, it's better to just get a new alternator since removing and replacing it, on the V8 anyway, is a lot of work. I got a new Valero (French company but made in Mexico) OEM alternator for under $200 locally. Most places charge a lot more and I think I just got lucky. Also, don't go the rebuilt alternator route. I tried that and the one I got had a dud regulator in it that was worse than the one it replaced - full refund given. They don't replace them when they rebuild the alternator, but should.

twh

Start by replacing your battery. Your mechanic seconds that motion.

gwf545

Good point, That is the first thing to do, so I had assumed that was done or checked. It should at least be stress tested, which can be done at most auto parts stores for free.