I have a 2006 Cooper S hardtop with 143,000 miles on it. 3 years ago, a reputable repair shop told me the alternator was going bad. (I don't remember what I was in the shop for, but that's what they told me). They put a brand new one in.

Fast forward to August 2020 (a few weeks back), and that alternator was on death's doorstep. I barely managed to drive the car to the dealership. The dealership confirmed the alternator was nearly done for, and quoted me $1500 (parts + labor) to replace it. That almost totals the car as far as I'm concerned.

So I take yet another risk: I drive my dying car to a different, non-dealership repair shop and have them put in a used alternator for $700 (parts + labor). They do, and all seems well. Until today...

Today, I start up the car, and immediately notice... The alternator light is on. And the power steering is out, a dead giveaway that the car is not getting any juice and needs to cut power to any and all amenities. I can't tell you the dread and despair I felt. This car is going to bankrupt me. After turning the car off and back on again, the issue resolves itself. But I know it's only a matter of weeks or days before this alternator is toast too.

Can anyone help or offer suggestions of why my car is doing this?

 

How old is your battery? maybe the alternator is getting worked harder than usual to keep it at an acceptable level?

My other thought is that you've gotten unlucky with aftermarket replacement alternators. Do you know what brand(s) have been put in? Denso is the OEM, when my alternator failed, 2 or 3 years ago, I replaced it with a denso re-manufactured alternator and it's lasted well for me.

My thought process is that 3 years ago they put an aftermarket alternator in that failed prematurely, and then you just got unlucky in august using a used part with an unknown history. The alternator isn't that hard of a job if you're up for a little wrenching, the hardest part is putting the car into front end service mode, and then putting it all back together again.

 

In most cases it's going to be one of these 3 things:
-Alternator itself (normally when they go, they go)
-Battery (have it not only checked for proper voltage, but load tested as well)
-Bad or Loose ground. (Can easily overwork an alternator)

 

Please tell us you were actually having charging system issues before bringing in the car, i.e. battery dying, slow cranking, low charging voltage etc and that they didn't just "find" an alternator problem out of the blue...

 

The battery is a good point; It's almost 4 years old. Though that said, when I had the car in the dealership for diagnosis, they didn't mention the battery (and they usually don't hesitate to say a part needs replaced because $$$; Hell, I'm surprised they didn't at least lie and say the battery was bad too just to sell me a new one). And the car doesn't really have any symptoms of a dying battery. Then again, a battery is relatively cheap and very easy to install, so maybe I might as well try...

It's possible I've just had bad luck with the alternators, but that would be quite a coincidence; Two alternators spontaneously dying within a few weeks of each other. So I think the most prudent thing for now is to assume something is over-taxing the alternator. That said, I don't know the brand of the alternator from before or the brand of the alternator in the car right now. I feel a mix of anger at myself for being so negligent, and anger at car repair shops because I just wish they could be trusted and I wish every car owner didn't need to be a walking encyclopedia of car parts, brands, and engineering.

I looked back in my records; I was there due to a nasty sound coming from my car, which the shop determined to be the drive belt tensioner heavily corroded. They also told me the alternator was suffering from corrosion as well, and said it should be replaced for that reason. I realize now that was probably a bunch of complete crap. The repair shop was a Midas with 4.6 stars on google from over 200 reviews.

Fun fact, I actually have been trying to sell this car. I had the alternator replaced to get the car in running condition to sell it. A big reason I want to sell it is because I simply cannot own such a complicated car anymore. I love it to death, but it's just impossible to rely on repair shops, so the simple fact is, I need a car that I can work on myself, or no car at all. It seems to me there's no alternative. I am more than willing to work on a car myself, but I don't have a garage or a lot of tools, or much car knowledge, so it's not very practical to do repairs on my Mini where it seems every little thing requires putting it into front end service mode.

 

OOF.
Understand 110%, welcome to the Bimmer step child nation. Good news is if you want to try and sell it here, the ad price is right, and you're among friends who can see past the car's current issues and proffer a fair price to take it off your hands. Worth a try anyway.

Edit: pro-tip: Toyota or Honda, preferably with a manual. Million mile cars if you change the oil. Avoid used hybrids and CVTs.