Replacement alternator for E53 4.8is

[X5only]

Originally Posted by hias

I have replaced the alternator of my E53 4.8is a few weeks ago and it is whistling quite loud.
Additionally, the new one is regularly causing DME error code 2E95 (communication to alternator lost).

Has anybody here already replaced the alternator and managed to get an alternator which is not whistling and not causing DME error code 2E95?

One thing you should check - is the data cable connected to the alternator correctly and verified not severed?

[hias]

Both the old and the new alternator are whistling. Already checked that the data cable is connected. 2E95 error does not appear immediately. Yesterday I was driving for about 90 minutes and the 2E95 error appeared 3 times within that time.
However it is only an error code inside the engine ecu and there has never been a warning light turning on.
Alternator is charging fine. 14,4V.

Old alternator never caused any error codes.

Here are a few videos I took today:

1) https://streamable.com/wh6it
2) https://streamable.com/mqwye
3) https://streamable.com/rb5lo

Maybe somebody with a replacement alternator can also take a similar video, so we can compare it.

[andrewwynn]

You need to isolate 100% proof positive the source. I would take off the serp and run for a brief shot to make sure you aren't listening to an air leak and the sound vanishes when the alternator is not spinning.

The power steering pump is right there as well and possibly more likely to make a whirr sound that i'm hearing on the video.

if you had a shorter serp belt some creative winding you could isolate one at a time to determine which accessory is whining.

there are a lot of sounds in that audio but best guess the whistle you are hearing is about 1700Hz at idle and about 3800Hz when you rev.

If you measure the diameter of the crank pulley and the alternator pulley you can compare that; if for example if it's 2 to 1 ratio and the revs are going from 850 idle to 1900 that would make sense if the sound is coming from the alternator but it felt like the rev was much higher than that.

Considering somebody else's recent failure of a fan clutch, check that out ; see if the fan spins freely when engine is off, then I would block the fan with a piece of foam (i've used foam pipe insulation in the past) and block the fan from spinning (if you have a clutch fan of course NOT if electric); what i'm seeing is a sound that changes frequency NOT in proportion to the RPM which would suggest NOT part of the spinning accessories.

[hias]

When running the engine without the belt, the sound is not there.
Already tried that a few weeks ago.

Revs were not above 2000 in video 1 and a bit above 2000 in video 2.

Sound is definitely coming from the alternator.

Please take a look at video 3. I think the frequency of the sound is proportional to the rpms

Also, this is an electrical noise. I have installed a Chinese tv module and this module feeded the speakers exactly with that noise so I disconnected the tv module.

[andrewwynn]

Ok that's interesting. I was going to say that sound reminds me of electrical interference on the radio. Frequency definitely proportional to RPM you actually just confirmed that. I thought you reved higher than 2k.

The VR is not outputting clean voltage. How old is that alternator? An o-scope is the way to determine where the noise is. If you can hear it without amplification that's a big internal issue usually (like open winding)


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[hias]

Yes, however the sound is coming directly from the alternator, not the speakers. If windows are closed while driving it is only slightly hearable on lower speads and lower rpms. On speeds >35mph or revs > 3000 rpm engine and/or wind noise will be louder than the alternator sound.

The alternator (voltage regulator included) is about 1 month old and is whistling from the beginning. However the old alternator was also whistling.

That's why it would be great to compare my sound with other people who have already replaced their alternator with an aftermarket one.

Of course Icould measure it with an o-scope, however I don't have one here and I think we already know that the problem is inside the alternator

[andrewwynn]

Can the local auto parts store do an on-car test? By internal I meant pre voltage regulator. The VR can possibly compensate for one of the three windings being compromised by modulating the field current once per revolution. That pulse of change of magnetic field will make things vibrate and also be audible through the air. I would hope a decent tester would notice if the output is lumpy and fail the unit.

New unfortunately is no guarantee of not defective.

We own two X5 both with M54 and air cooled alt so I can't do a direct comparison but I've worked on M62 with likely the identical alternator and I would have noticed that whine immediately.


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[hias]

I will change the alternator anyway because it is not only whistling, it is also causing an error message in the engine ecu (unlinke the old one), so no need to spend money for tests.

M62 engine has a different alternator (a watercooled one) unlike the N62.

Just want to ask about your experiences with aftermarket alternators for the N62 engine.

So if anyone of you has got an E53 4.4i N62 or 4.8is and already replaced the alternator, it would be great of you can take a video :-)

[andrewwynn]

I thought you said you had water cooled like M62. My buddy has N62 he might be able to see if it whistles. If air cooled it would be possible the cooling fan causes the whistle but if there is electrical noise in audio equipment there has to be a problem in the generation


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[X5only]

I have 2005 N62 4.4 and the alternator is definitely not whistling - I'll post a video tonight. It's an after market alternator installed way back in 2011. The only whistling issue I have is when my dynavin Bluetooth is on. The whistling is from the speakers.