NOT THE ALTERNATOR, NOW WHAT??

[Bmwtvboy]

I just completed out of car test twice at Auto Zone. The machine claims the 218 K mile alternator is fine. When it was in the car it Voltmetered 11.3 volts at the X5 jump site and at the battery. Where do I go next? I have to reinstall the alternator. I didn't get to test the unit at the rear post of the alternator because I couldn't get to it without removing the M.A.F. sensor.
Histoy: 2months ago I removed the air shocks, It's only a rear air setup, but left the compressor connected- the pressure tanks were also disconnected. Could this be causing a charging problem? Is the Autozone thing wrong?
The X has been fine up until last week breakdown.
The dash lights are all on when the battery light is on, cruise doesn't work.
THe SES light is on too. The radio MID is diconnected because it supposedly had a short. Another shop said it was a module in the glove box. But for over 8 months since disconnecting the radio MID everything was fine. Then, I did the suspension upgrade to springs. Where do I go from here?

[srmmmm]

I think the alternator testing machine was wrong. 218K miles on the original alternator is more than I've ever seen on this forum. Mine went at 126K. With the engine running, you should be seeing something like 13.8 volts at the battery posts.

2002 X5 3.0 312,300 miles
2014 428i 22,800 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

1970 Firebird - Under restoration

[oldskewel]

I don't know about your particular alternator or that autozone machine or the guy who did the test, but I have had experiences over the years that make me not trust those off-car in-store tests at all. I even think they damaged my alternator one time.

If the on-car test shows low voltage, I might trouble-shoot around that, but would still expect the alternator to be bad, especially at high mileage, like srmmmm says.

At the very least, remove the back cover and inspect the brushes. Trivial to do, and likely to find the problem. You can also just spin the pulley and feel for any roughness or excessive play in the bearings (although you probably would have heard it if there were a big problem with the bearings, and bearings would not directly affect your voltage output).

[squidzilla]

I know you do not want to throw parts at it, but with your mileage I would just buy a new one or buy the kit old skewel linked to on ebay in his other thread (awesome btw)

I think the alt is on borrowed time if it is not bad with that mileage.

[StephenVA]

Any life after 150K on an alternator is a day with sunshine.

The only way to test Alt output is to load test to specific AMP value and read voltage,total amp output, and diode results. Reading volts will show regulator control/alt output but not total capacity and capabilities of the said unit. Testing must be done at 1500 RPM and again at 2500 RPM. The Autozone tester will find dead ones, not intermittent functional Alternators (brushes, reg, winding etc). They only do a pass fail test based on the user's skill set - poor at best.

I personally would recommend replacing the Ign SW (if it is the OE one)and the Alternator, as they both are due. When these two parts start to go away, they will give you all kinds of weird failures and operational errors. Cheap insurance and cost of normal ownership.

Both are easy to do with the right tools. Nothing fancy just hand tools.