Short version, longer for another time or downthread, the alternator on my 2017 F56S is going bye bye. Or, more accurately, the voltage regulator/rectifier is apparently failing, which likely means one or more diodes within are failing. Measured voltage output is all over the place, including going too high and too low depending on however it is feeling at the moment. The battery and car in general are suffering in various weirdo ways as a result, with the common denominator appearing to be slow death by lack of reliable alternator output.

I have replaced voltage regulators and brushes within alternators before. No biggie -- in principle.

BUT I need to figure out exactly what part number from what manufacturer (BMW does not manufacture alternators, someone else built this thing) -- is in my F56S.

If I can ID the *real* details on this alternator, I can find my way to whether the regulator is removable/replaceable (likely is), and then find my way to getting that part (along with brushes).

I definitely can pop this alternator out of the car and disassemble/service/reassemble/reinstall it (vs forking over between $660 and $1100 for a new genuine BMW/MINI part, or taking a chance on a used part, or $300+ for a new aftermarket part). Just need some help identifying which OEM BMW sourced this alternator from and that OEM's part number.

Anybody got some part intel?

 

Ohai look what I found... and I actually know this company (Maniac Electric Motors)

https://www.maniacelectricmotors.com...6720-6721.html

 

I was about to send that link!!!

No rectifier, but it sounds like a regulator issue anyway.

Also, our F56 is actually a BMW X1, so you can chase that too.

 

I bought a high-output alternator from the same firm over a decade and a half ago for my 1995 not-BMW/MINI. Still running it. And I can say from firsthand experience that they both know their stuff and stand behind their products. Good shop.

 

Turns out my F56S has a (genuine BMW) alternator that doesn't match that kit's spec. The kit is for a 180A output alternator -- but what is in my car has this on the label (amazing that it is both visible from the top and still attached):

BMW Denso
14V150A
S:7640131-03
104211-8181
07T26

Getting curiouser by the minute. We'll see what Maniac says.

 

At least, they have the regulator!!
https://www.maniacelectricmotors.com/80904618.html

 

Regulators would be the same, it doesn't regulate amperage, only voltage.
Amps are based on stator size.

 

Appreciate that clarification on the regulator vs stator. Had forgotten that. Haven't had my head in an alternator since maybe 2010 -- gonna go do a little read-up.

So here's the latest, and I have to give a give a gigantic +1 to Maniac Electric Motors here.

Backstory, I was all over getting a kit from them as soon as I realized they had one, because -- again -- I put a high output alternator from them in my 1995 not-MINI. That was back in 2007 or so. That alternator is still in that 1995 vehicle, which now has 351K miles on it. Maniac has stood by its product the entire time, even doing an out of warranty repair at a cost that was plenty reasonable, when (I figured out this root cause later) a fairly invisible crank pulley problem was wobbling the drivebelts to death and messed up the alternator's bearings.

As iffy as I am about putting aftermarket electrical in the MINI, mainly because the MINI is so sensitive about such things, I would throw pretty much any Maniac electrical product into my engine bay. No question. If they told me I needed a disco ball under the hood I would seriously entertain the thought for at least half a moment on general principle.

So I reached out to them about the fact that the kit (Maniac part number 20854RK) that *looks like* it's for the alternator in my MINI based on vehicle spec, but doesn't reference the same part number or amperage as the label on the alternator I have. Electrical being as particular and specific as it is, Maniac knows more than I do so I figured I'd make direct contact and ask.

Here's what I got back.Now get this -- that new part and new kit number hadn't even hit their website yet (they will). So this was seriously up-to-the-minute information, with up-to-the-minute handling.

I was reminded of why Maniac had such strong recommends before I found them, and why I came to love their shop. Heck, it turned out I was even talking to the same person who I worked with on that original high output alternator on my other vehicle, and on its bearing issues. I'm about ready to send them a cake.

Oh, did I mention the rebuild kit is $59? Total score. If you have the skills to open your alternator and replace specific internals, and the alternator hasn't been burned to high heaven by waiting too long, it's worth a shot when the alternative is (at least) a few hundred $.

So I'll get the new regulator & kit (which includes bearings, brushes, and brush assembly) next week. Looking forward to doing the actual work on the car, probably next weekend (lots of stuff to do in that right front quadrant -- motor mount replacement, washer fluid leak repair, possibly serpentine belt replacement, possibly idler replacement -- not sure yet but I don't want to go digging around in that quadrant of the engine bay more often than I have to). When I get to all that I guess I'll document the heck out of it, including the alternator disassemble/reassemble.

 

Clean the commutator with a scotchbrite pad, not emery cloth, and clean out the slots of residue with a toothbrush.

 

Final update:

(1) fixed the issue that had me chasing the alternator around (problem was not, in fact, the alternator).

(2) I am glad I changed out the alternator brushes. They were about 1/2 gone. Replacing the regulator/controller (the regulator is DME-controlled) was not possible as a practical matter because it has a contact that is in turn spot-welded to a stator contact. Sure I could get it off and get another on with some effort -- but since things are working, it's not really worth tearing the thing apart.