Thanks...upallnight. I don't remember exactly when the battery was replaced but it should be at least 40k miles ago. Currently 141k miles.
Just checked battery voltage again it showed 12.3V now.
I am still wondering why would this happen right after the mechanic did some work on the x5??:dunno:

Suggest you add the year and engine to your signature.

Depending on the engine there is a power steering hose that runs from the pump up and in front of the alternator. It is possible that power steering fluid got on the alternator.

Number of years old usually determines the life span of the battery. Depending on the quality of the battery, conditions of the environment and normal load on the battery and as a general rule, it could fail anytime after 3 years.

Suggest you have the battery load tested. A load test is the way to determine a good or bad battery. As Upallnight posted a resting 11.5 after the vehicle has been running for a half hour or more, with a good alternator indicates a bad battery.

If you unlock the cluster you can monitor the alternator output. If the alternator output is consistently in the range of say, 13.8 to 14.3 it is probably OK though it could have stopped charging for a time due to power steering fluid getting into it.

I think the best practice is that there are no coincidences when something like this happens. BMW electronics do strange things when the voltage is low. Are there any other low voltage symptoms?

Thanks bcredliner !
It is 2005 make, also updated my signature.
Yes that is exactly my point. It cannot be a coincidence. I don't see any other low voltage symptoms.

I was looking for the menu to check Alternator Voltage. But could not figure out the menu #. Is menu 9 for Battery voltage?

I am going to unlock cluster and check one more time now and post back.

Thanks

Yes I was able to find one video yesterday for E53 as well Thanks

REGULATOR DIAGNOSTIC TEST
 

Greetings,

I am new here and wonder if any experts know what a continuity test on regulator reads. I have 03 X5 4.4 with the monster water cooled alternator, and before I purchase regulator which I suspect is bad, had already put new battery in a couple months ago. Battery light came on after a 200 mile highway run at 80 mph as I like to blow out engine once in a while with a good highway run. Ran beautiful, until battery light popped up, barely made it back having to shut down all electric, pulled daylight headlight bulbs and tried not to use brakes as much as possible, and got back home. Nothing worse than getting stuck out of town.

So put alternator test on and no output, charged back up battery which did drain to point it wouldn't start, checked battery, it reads 100%, so looks like alternator. Not an easy job, changed one on my 545i a couple years ago, replaced with new, so as I had old one, I opened it up to see if I could repair it with regulator. My question is, anyone take continuity readings on the two terminal connector? I get reading one way, reverse leads on meter and no continuity and I can't remember, but recall I shouldn't see any continuity between terminals either way, so anyone remember or have experience on regulators? Hate to go out and buy a new alternator if it is only regulator. How long do these alternators last normally?

Thanks,

Why bother testing it. They are inexpensive and really the only thing that goes bad, normally. I have never had windings go bad on me.

Thanks, it is the labor and time issue more than just replacing it and see if it corrects problem. This is a water cooled alternator, a real PITA to remove and change regulator, so if it is diode bank, don't want to waste money on regulator, not cheap on this unit, and no windings, totally different than standard alternators.

according to WDS, the battery light comes on when the balance on the rectifying diode bridge is disturbed. there are 4 diodes, connected in a specific way (google rectifying bridge), so if one burns, the balance is off... it has been a while, so i can't recall now the details of repairs, do a search for M62 alternator bridge repair (here is one - http://www.bimmerforums.com/forum/sh...led-alternator), so you might be able to repair it.

Thanks, will check the diodes as well, just didn't want to take a chance to replace regulator alone, only to find out after putting it back together that a diode could cause same battery light issue.