Repeat Alternator Failures???

[BruceWillis]

Wondering if anyone can shed some light on my latest issues:

TL;DR: Bought car, drove it 1000+ miles, wouldn't start. Replaced battery. Alternator light came on. Replaced Alternator (Bosch Reman). Replaced Coolant lines. All good for a week. Mystery whine from engine bay. Alternator light comes on. Not enough juice to start. Battery voltage sub 12v.

My questions are: is it likely for a reman alternator to go in a week? Are there other things (faulty grounds/connections) that could be causing the alternators to fail? Could the mystery sound be from the alternator, or should I investigate something else? I'll be taking it back to the shop tomorrow; just want to see if anything is glaring to more… seasoned.. bimmer owners.

A little back story for those who may find it helpful:
Purchased 2001 325xit (manual transmission) in Denver. Smooth until Vegas, then the car wouldn’t turn start (headlights/indicators flashed, clicked). Was able to pop the clutch and finish the rest of the trip to LA without turning the car off. Figure it was the battery, alternator, or starter, but there was no red alternator light.

Replaced the battery, and all was good until alternator light came on. Had the alternator tested at O'Reilly's and got low voltage reg and low power output readings.

Replaced alternator with a Bosch reman. While the car was in the shop I also had coolant lines replaced due to leakage.

Over the course of the following week, a whining sound (like a toy motor) started coming from around the pulleys. It got higher pitched as RPM went up. Seemed to get slightly quieter as the engine warmed up, but always there (in gear or neutral). Noise got louder throughout the week.

Today, the alternator light came on. Was able to drive home. Using the tests on the dash (test 19/9), the voltage across the battery was 10-11v. Got slightly higher (11.5ish) as I started the engine and revved. Went to turn the car on later and there wasn’t enough juice.

Any help would be greatly appreciated. Thanks!

[MIKYZZ4]

Inspect all belt tensioners and pulleys for grinding/wobble,
Also that alternator may be defective.

[bmwdirtracer]

Until six months ago, I had never seen a bad Bosch factory reman alternator (from a black Bosch box). Since then, I have had two. (I do this for a living).

And, just this week, for the very first time, the Bosch alternator I ordered in came in the same box, except the lettering said "100% new" ! I've never seen a brand new Bosch alternator offered anywhere before.

Anyway:
Check, or better yet replace, fuses 30 (7.5A) and 34 (5A). Make sure that with the ignition on, both the green/brown and the blue wires at the alternator plug are getting battery voltage.

Also, make very sure that all the main hot and ground wire connections are clean and tight. If the alternator isn't correctly connected to the battery, it can toast the alternator almost immediately, because it goes WAY overvoltage. (This can also fry the car's computers.)

These connections include both ends of both battery cables, the B+ terminal underhood, the big bolt (two wires) on the starter, and the main feed at the back of the alternator. {The wire from the back of the alternator only goes to the starter, where it is bolted together with the feed from the battery and B+ terminal....therefore, if the starter bolt is loose, the alternator isn't connected to the battery}

Also check the main engine ground wire, at the right-side engine mount.

If all these connections are good, and you have voltage at the blue and green/brown wires, and you don't get 13.5 + volts, you need another alternator.

And, as Miky indicates, make sure to check all the other pulleys while you have the belt off. You can also listen (carefully!) with a stethoscope, to each pulley, with the engine running, belt on.

[jclausen]

Have a shop run a complete charging system test using the right equipment

[BruceWillis]

Thanks for the advice! Is there a way to access the starter connections without removing the intake manifold?

[bmwdirtracer]

Yes. It's not fun, and it's mostly by braille. A mirror on a stick, and a good flashlight will give you a little bit of a view, from underneath the car. Did the previous owner recently replace the starter? If so, that main hot wire with two big hot wires attached is a likely culprit.

Make sure, if you go poking around with tools near that bolt, that you have disconnected one of the main battery terminals !

[BruceWillis]

Quick update:

Battery was dead. Got a jump start while in voltage-monitoring test mode.

Pre-Jump: Voltage at 9v
revved engines: got up to 12v,
started engine: voltage at mid 10v
Engine Ground: Wired a temporary engine ground from engine to negative terminal above strut tower: after brief spike of about 3.5v, voltage settled to around 12v
Removed ground: dropped voltage down to 10v again

could a faulty ground be leading to premature alternator failure? I know very little about electrical systems so I'll be taking it to a shop next week instead of messing with the exciter wire/connection points by myself. Any tips on specific things for them to investigate would be greatly appreciated. Thanks!

[MarcoZandrini]

That voltage drop after removing the temporary ground means that the factory ground is likely badly corroded. An alternator has a limited current capacity. Attempting to get more current out if it can damage the alternator. However, I’d investigate the grounding issue first. A 3.5VDC spike is a definite indication that the engibe ground is bad. Also, a lead acid battery is permanently damaged when it’s fully discharged. The chemistry damages the lead plates, thereby reducing the battery’s capacity. I think you need a new battery.

How do you know the alternators are bad? The alternator’s ground is the engine. If the engine ground is bad then so is the alternator’s. Fix that first, buy a new battery and proceed from there.