Bosch reman alternator seems to have failed at 12,000 miles (540I6).

[Santaclaus4]

I installed a Bosch (reman) alternator just over a year ago in my 540I. It has just barely 12,000 miles on it and it seems to have failed.
Last night I noticed my lights seemed a little dim so I checked voltage at the cluster. It showed 11.6 and was dropping as I drove home. It got down to about 11.2 volts at the cluster. I shut the car off for a bit and restarted it. The voltage was 13.7 for a few seconds and dropped quickly to about 11.2 again.
Today on a cold engine (after starting) the voltage was 13.7 so I took it for a drive to the store. In "country" miles, the store is about 10 miles away. As the engine warmed up, the charging voltage dropped. Once the engine seemed to be fully warmed up, the voltage dropped to 11.6 and held for a while. By the time I got home, the voltage was 11.2 again.
FWIW, at first as the charge voltage started to drop, It would still increase or decrease with load and RPM. I could turn on the seat heat and it would maintain 13.5 volts. At idle with the seat heat on the volts would initially drop to about 13. As the engine reached full operating temp, it would no longer maintain voltage.
Basically it looks like it fails with heat.

Unless someone has a different idea, I'm gonna replace it. I bought it from FCPEuro so I'm not expecting any issues but I want to make sure I am returning a failed part.

Also, Is there a preferred brand of reman alternator?

[StephenVA]

Only on of two areas to confirm failure
wires tight and clean connections check with volt meter at unit
regulator failure due to cheap parts or slip ring not cleaned properly
welcome to reman units quality control

[JimLev]

No slip rings on the water cooled alt.

Before you pull it out check both ends of the engine ground strap on the pass side between the engine mount bracket and the frame.
A few years ago I found a lot of corrosion on one end of it where the bolt held it on. I was surprised as my car has never seen winters or snowy salty roads.

[Santaclaus4]

The wires are confirmed to be clean and tight and the ground strap on the engine is tight and appears to be corrosion free with a light coating of engine oil from the leaking valve covers to act as a corrosion preventative (ugh).
I hate to pull it out because the coolant is only a year old. Oh, well... I've tried to save coolant before but it's difficult to keep all the contaminnts filtered out. For the money, I'd rather just replace coolant anyway.
On the bright side, I replaced all the pulleys, hydraulic tensioners, and belts (and power steering pump) last year so there shouldn't really be any "while I'm in there" items.

[Akash3230]

I replaced the alt on my e39 and e38 both times the first alt was bad would charge when engine was cold but would stop charging. Had to get replacement alt. Both were bosch remans


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[Santaclaus4]

I replaced the alt on my e39 and e38 both times the first alt was bad would charge when engine was cold but would stop charging. Had to get replacement alt. Both were bosch remans


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How many miles are on the second remans? Are they holding up better?

[Akash3230]

Since replacing both on the e39 30k e38 about 6k


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[geargrinder]

I've had great luck w/ Bosch remans on multiple cars - both alts and starters - but its not unheard of to have a bad one once in a long while. Just as a 'tick the box' item - did you check battery connections too? No water in footwell etc? An intermittent elsewhere in the car could cause that kind if up and down stuff too.

I save coolant all the time BTW. Sure if its old I don't bother but when youre doing a job and all new stuff went in a few months or even a year ago and its crystal clear... screw that I'm saving it, stupid to waste it.
This is all probably "duh of course that's what I'd do" for you santa, but FWIW I drain as much out from as clean a location as possible, then I strain it for any big debris, then I let it sit a long time for settling purposes, and decant the top off, throwing away the last inch or so. Then just top off w/ fresh to account for the stuff I tossed. I keep a couple dedicated 5 gallon super clean buckets just for the purpose.

[JimLev]

Mine is a Bosch reman too, now about 8 years old with maybe 50K on it.

You said to checked the ground strap at the engine side, how about at the body side?

[Santaclaus4]

Mine is a Bosch reman too, now about 8 years old with maybe 50K on it.

You said to checked the ground strap at the engine side, how about at the body side?

I'd like to tell you that I did but I can't picture it so maybe I didn't.

I just this minute got done ordering a replacement for the replacement alternator from FCPEuro. It turns out that I never sent them my core last summer so when I get the 'nother replacement, I can return two alternators. One under warranty and the other a core (for store credit since it's been a year).

[Santaclaus4]

I've had great luck w/ Bosch remans on multiple cars - both alts and starters - but its not unheard of to have a bad one once in a long while. Just as a 'tick the box' item - did you check battery connections too? No water in footwell etc? An intermittent elsewhere in the car could cause that kind if up and down stuff too.

I save coolant all the time BTW. Sure if its old I don't bother but when youre doing a job and all new stuff went in a few months or even a year ago and its crystal clear... screw that I'm saving it, stupid to waste it.
This is all probably "duh of course that's what I'd do" for you santa, but FWIW I drain as much out from as clean a location as possible, then I strain it for any big debris, then I let it sit a long time for settling purposes, and decant the top off, throwing away the last inch or so. Then just top off w/ fresh to account for the stuff I tossed. I keep a couple dedicated 5 gallon super clean buckets just for the purpose.

Oh yes, I've checked battery connections. I had a dead battery a couple months ago and replaced the FSU as a precaution. I still haven't gotten around to pulling the passenger seat to look for moisture.

I've saved coolant before and tried to strain it through pigmat but that just doesn't work. Since this is pretty new coolant I might try to let as much as I can drain into a couple old (clean and dry) milk jugs.

[philly98540]

I do what GG does and save the coolant. I use one of those mud pans to easily collect the coolant as it drips down from wherever.
https://www.lowes.com/pd/MacCourt-Dr...hoCSy8QAvD_BwE

I let it sit in the pan as I get the work done on whatever. I pick out any floaters, then decant into a bucket leaving any crumbs in the pan. Let it sit in bucket for a bit, then pour into the rad. Pretty much same as GG. Works excellent.

Sounds like a bad alternator, but check what the guys have said. Good luck.

[geargrinder]

Yeah - I also do what Philly does when he does what I do....

AKA I use the big old cement/mud pan too... although thats usually when I'm doing a 'big job' and have to pop multiple hoses and crap that will leak all over a broader area... if its just the radiator for instance and its controlled disconnect of the main hoses, usually I can get away with the buckets...

[JimLev]

Yeah, I also do what Philly and GG does when they do what I do.
If my coolant is pretty new no reason to toss it.
I'll filter it before I put it back in the radiator.

[Santaclaus4]

Yeah, I also do what Philly and GG does when they do what I do.
If my coolant is pretty new no reason to toss it.
I'll filter it before I put it back in the radiator.

I'll give it a try. That means I'll do what you did when you're doing what they're doing which is what you did...

[blarf]

Oh yes, I've checked battery connections. I had a dead battery a couple months ago and replaced the FSU as a precaution. I still haven't gotten around to pulling the passenger seat to look for moisture.

I've saved coolant before and tried to strain it through pigmat but that just doesn't work. Since this is pretty new coolant I might try to let as much as I can drain into a couple old (clean and dry) milk jugs.

I've been watching too much of the South Main Auto guy's videos so bear with me. Did you actually check that the ground strap can carry current?

https://www.youtube.com/watch?v=fWdYo2uaSzo

It's unlikely, but still possible, for the cable(s) to rot out internally. With the symptoms you've described I'd certainly expect a bad voltage regulator, but it can't hurt to test the wiring before you pull the alternator out.

[Santaclaus4]

It's unlikely, but still possible, for the cable(s) to rot out internally. With the symptoms you've described I'd certainly expect a bad voltage regulator, but it can't hurt to test the wiring before you pull the alternator out.

I work on electronics/avionics at work and you are totally correct. I have seen many times where a wire shows continuity but won't actually take an electrical load. It's also common at my job to find a ground that look perfectly good but have a poor connection.
The symptoms point to a defective voltage regulator and my cursory inspection of the connections and ground points tentatively supports the conclusion.
Basically, I have "target fixation" on the alternator as the cause.

[Santaclaus4]

BTW, even though I work on electronics/avionics (at an airline) for a living, it doesn't mean I'm good at it or even have all the answeres. I have no problem with people asking me questions about what I checked, etc. I learn stuff from people on here that I didn't know like using a fuse as a shunt to check current draw. I mentioned that to my co workers and some knew you could do that, and others didn't.

[f355spider]

OP still have your receipt? Bosch reman used to have a two year warranty, I would check with the seller.
My first replacement was at the BMW dealer (kinda urgent)...it was reman by Bosch and lasted about 140k miles until the voltage regulator failed and I got a "free" replacement from BMW a couple years ago. "Free" being the alternator, coolant, a hose, and clamp. They charged me full book time of around 3 hours labor, plus 3/4 hour diagnostic time (I argued to no avail on the diagnostics, telling them the OBC showed low voltage, how hard is that?) 3.75 hours at $175 an hour...

[Santaclaus4]

OP still have your receipt? Bosch reman used to have a two year warranty, I would check with the seller.

Yes, I bought it from FCPEuro a year ago.

- - - Updated - - -

The replacement alternator is supposed to arrive tomorrow.

[Santaclaus4]

I got the new alternator installed. I decided to not re use the coolant since most of it went in my mouth. Note to self: next time take a couple extra minutes to remove the radiator shroud.
I'm gonna try the clutch fan delete for a while since I dropped my fan on the floor and broke a blade.