Alternator failure - probably
 

Driving the X-box back from son's high school last night. Battery light was flickering. After a few minutes it was flashing more regularly, then the ABS and brake warning lights came on. A minute later, the transmission failure lamp came on and there was no power. Limped it home, switched off and it wouldn't re-start, only click. Opened the hood and there's a nasty electrical burning smell.


It started up this evening. Battery voltage before starting was 11.25. After starting, it went down to 10.5 and dropping. Turned on the AC blower and it went to around 9. Electrical burning smell again.


Since I want to R&R the OFHG, might as well do the alternator. This car is really hitting the 'bathtub curve' hard.

- If your signature is correct, then 160,000 km = 100,000 miles.

- My 2006 X5 6spMT with 130K miles still runs on original alternator.

- Check what you have in the car: it is either Bosch vs Valeo.

- Do NOT buy rebuilt alternator (rebuilt quality is bad). Best NEW alternator.

- Look online, it is about $230-$250 etc.:

https://www.rmeuropean.com/Make/BMW/...?catalogID=006

I rebuilt my valeo for $20. Needed new slip rings and brushes. Your description of failure mode does exactly describe a dying alternator


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It's the '04, not the '06. Metric tonne of kms on this one. I'll be tearing it down for repair, and if it's not burned up may fix it myself.

- If you want to rebuild yourself, then bimmerfest E39 5-series forum has a nice DIY for Valeo alternator.

- Replace the entire Voltage Regulator, not just the slip rings.

- Bearings: Nachi, NTN, not the Chinese bearings.


Anyway, search for that DIY...

V8 here. At 152K right now, 18 months ago, I put it it's 4th alternator. So figure maybe around 136K.

You got luck OP. When it goes, it goes sometimes !
And others, well, you get the pre-advance symptoms.

My buddies alternator died last week (4.8iS). Similar symptoms, he's around ~73k miles. Tried giving him a jump, vehicle started but once you tried to drive away it would die.

Your buddy's battery is drained as well so it needs a charge and then he could drive all day until the voltage drops to 9.6 volts and the computers/ingn/etc no longer function.

I should mention the X-box hadn't been driven in a while and the battery may have been low to start with. But I'd have not expected it to kill it in 5km.

I had the same exact issue. It turned out to be a bad voltage regulator on my alternator. 20-30 dollar replacement. Been good for over a year now.

Most failures are
Regulator
Brushes (worn out or not connecting)
If you DIY it is not too hard
Trick #1 Smack with soft mallet, see if it works as rust, dirt, carbon tracking builds up on the shaft. The brushes are spring loaded and loose their ability to touch the center spinning shaft.

Test your battery ASAP as you need a fully charged battery for an accurate charging system test.