Alternator on the way out
 

Hi guys,

new to the forum, but did some research about this problem.
I got a beautiful 2005 X5 4.4i, fully loaded, except Nav and Air Suspension.

Two days ago, during driving on the Highway, some lights on the dashboard came on (DTC, ABS, Fasten Seat Belt, Airbag, Transmission.....) So, I stopped, shut the engine off, tried to restart, nothing, not enough battery power.
After I waited 10 minutes, I could start the engine again and the lights were off and I could drive 100 km on the Highway without issue.

One day later, I drove and after 30 km, same thing happened and additional I lost the power of the engine (low voltage) and I was stranded on the side off the Highway, could not restart and ended up on the flatbed of a tow truck.

At home I checked the battery and it was only charged to 25%. Overnight I charged the battery and did a load test in the morning, absolutely fine, checked the voltage with running engine (and driving) and got between 13.8 and 14.1V.

I think, the alternator is on the way out, BUT is it possible that this happens intermittent???

Thanks for your attention.

Michael

I also have a '05 X5. My car completely shut down on the verrazano bridge on me. I was getting red battery light every time id start the car cold. Id change the alternator & be done with it. Its not the easiest job but its not too bad either.

Interesting is, I never got a red battery light............
@BigBody
Do you know, what your output voltage is with a running engine??

People report bad alternators with the light on, & with the light off. Must be a specific condition to set off the light. In my case, i believe the car would start & the alternator was lazy; not running. With the engine running it should be at or around 14v. Use the OBD menu so you can get an idea where the voltage of the battery is while the car is off, cold, driving, etc.

Once i changed the alternator my problem was completely gone. The bad alternator eventually killed my battery (seems your having a similar problem), thus leading to my car dieing on the bridge. Luckily i was over the crest, but yea... just nothing- hazards wouldn't even blink. Rolling with nothing but the machine lol... my mother was close by, jumped the car & guess what? Car ran fine all the way to the BMW event in the bronx we were heading to hahaha...how ironic... yea id replace the alternator & battery while you're at it.

BTW, if you have an '05 4.4i, you probably do have air suspension, just in the rear as opposed to 4 corners like in the 4.8's.

Confirm before replacing. OBC menu on the dash. If the voltage reads considerably > 13.8 and no dips < 13 it's just the battery. Additionally, it's a good idea to evaluate off yet starter is going before you replace a battery, though that doesn't seem to be the case here.

I quite often see people incorrectly diagnose the situation and replace both a battery and alternator when it was the starter the whole time.

A starter when failing can take a year to completely fail but pull up to double the normal current. It will "feel like" a weak battery. Hence the need to measure voltage at rest and driving to help determine which of the three are actually failing.

My alternator wore out a couple years after I got my '01, but it's an air coolle Valeo and eazy to change the brushes and slip rings so I just refurbished mine. About two years later my battery went. It will charge up to full voltage and start the car fine every time unless even a little charge was taken off the top (iPhone charging for 30 minutes required a jump start, the final straw was 8 minutes or hazard flashers couldn't start), then half a year ago or so, starter finally went kaput so I've went thru all three. I have the 3.0 so the mechanics of changing are different but the diagnostics are the same.

First get a good charge on the battery with a charger. If you have a good volt meter with min/max or ironically a really crappy one with an analog dial, hook it up between the jump point under the hood and the cig lighter (POS side at cig).

When you crank the engine the voltage drop is approx. 1/180 the current to the starter. Eg 225/180=1.25v. (I haven't run that test in a while the ratio could be different I'm pulling from cobweb memory). I will do that test again soon to compare with my new starter. I posted my original test results on xo to compare.

If you noticed hard slow cranks before starting leans towards starter, if you noticed no problems then after a short bit of engine off power use eg listen to the radio for ten minutes and need a jump it's the battery. If the symptom of random dash lights like abs came on when you are coming to a red light it's the alternator.

(Most likely candidates).

Look at the date stamp on the battery. They usually last about five years.

To directly answer this, yes. If the alternator is failing simply due to the brushes wearing out, it may reach a point where the shorter of the two brushes is just barely making contact with the slip ring. During that period, the alternator will work / not work based on apparently random conditions driven by temperature, vibration, etc.

But as mentioned above, it is odd that no charging light came on. That light is usually driven by the very simple condition that the battery voltage is higher than the alternator output voltage - so if the alternator is not generating that voltage / current, the light will come on. In the olden days, it was a simple wire and light bulb in the dash; more complex now, typically controlled by the ECU. So more careful testing will help you avoid replacing parts unnecessarily.

It will help to know:

• how many miles on your car / alternator (if not original)
• how old is your battery?
• do you have the high tech cluster (that displays written messages vs. warning lights)? If yes, any messages, such as "trans failsafe prog."?
• does your charging light come on when the car is turned on but not started?

I never got a single preview of a battery light on my dash. My first warning of my alternator going out was that my abs trifecta came on and stayed on about a mile from my house. I coincidentally previously had a major oil leak spray my poor alternator making It suspect so it was a prime suspect. From the OBC menu I was able to confirm voltage instability and pulled the alternator. Research led me to replacing the slip rings rather than the entire unit. Very glad I did because not only has my alternator been working fine for 2.5 years since, wife's alternator needed new brushes and I actually only replaced her brushes, no slip rings.

Yes, you are right, it has air suspension at the rear......

And today, I "caught" the car with only 11.4V during running, so, it is intermittent problem with the alternator, will change.....

- 164.000km (Live in Canada)
- 2 years
- trans failsafe came on together with Light for ABS, DTC, Airbag, engine died of low voltage
- yes, charging comes on

Interesting today
- I "caught" the car with 11.4 V with running engine and 12.4V without running engine, so, it is the alternator..


Thanks!

If you haven't already, read my thread about my alternator fix:

https://xoutpost.com/bmw-sav-forums/...nator-n62.html

Mine was one of the first N62's off the line. It had the original alternator which was fortunately superseded with one with an movable nut for the bottom bolt. That extra 3 or 4 mm of play made the replacement alternator I got much easier to install.

If you buy an alternator or just replace the voltage regulator, make sure that you align the adjustable nut flush with the inside edge of the assembly before replacing it. When you screw in the bolt, it will pull the nut toward the front.