SOLVED - Headlights pulsing.
 

I am out of town, and my wife sent me a text to tell me that the headlights on the X5 are pulsing. The dash lights are doing the same thing. After a few searches, it looks like the recommendations are either alternator or battery. The battery seems to start the car fine, and the alternator was rebuilt about 2 years ago. I do not know how old the battery is, but I would guess it has to be at least three years. Right now I'm thinking I should just replace the battery. Any opinions? Have any of you experienced this?

a tricky diagnosis especially from out of town. i would load test the battery, to see if thats the problem first, thats the easiest test. also make sure that before you start the truck, you have 12v at the underhood terminals (on the fire wall for the + and on the driver fender for the -), this will tell you if you have enough battery to start the show. there seems to be some belief that the whole instrument cluster goes haywire once the voltage drops below 9v or so.
if you can access the alternator plug at the rear of the alternator, check that the center pin (there are two plugs in there, the one in the physical center is the one you want) check it for 12v when the key is turned to the on position. this lets you know you have an ok alternator harness.
failing that, check the same underhood terminals when the engine is running, if you still have lower than 12v or a dropping voltage, then i would suspect the alternator is not working.
good luck!!:cool:

It's the voltage regulator and it's attached to the alternator.
Unlock your OBC and go to test 9.if you see the voltage going all over the place then go replace the VR and you should be good to go.
Good luck.

Can the voltage regulator be changed without removing the alternator? I replaced the battery today (it was at least three years old, and out of warranty, so good to swap before winter anyway). This did nothing to fix the problem. Used the diagnostics on the instrument cluster, and the voltage is jumping up and down. The high beams, dash lights, and HVAC fan are all pulsing like crazy. The xenon low beams seem to be unaffected.

Also - to ad to the above:

I scanned for codes with my Peake reader and there are no codes present. There are also no warning lights on the dash.

You will have to remove the alternator as the VR is right in the back of it.
Edit: take yours off and order the same brand and part #

Since pulling the alternator from this car is no small task - I called the shop that rebuilt the unit two years ago. They asked me to bring the car in and they would test it in the vehicle. Now I just need to pry it away from my wife for long enough to get it tested.

I just want to avoid pulling the alternator unless I have to. I still remember what a pain that was!

Assuming that you have the 4.4l, it won't have a replaceable vr. It's a water cooled version mounted in the lower timing cover.

If he has the water cooled one, then yes.My i6 E39 had a replaceable VR ; I still changed with a brand new alternator...

I thought watercooled one is on M62, and the others are all aircooled... maybe not...