Hello - I'm looking for some help please...

My Car:
- 2004
- base non-S
- 40,700 miles

Background to my original problem:
https://www.northamericanmotoring.co...per-non-s.html


Summary:
- Battery light came on in mid March
- Auto parts store connected charging system tool and determined battery was OK and system wasn't charging - we thought it was the alternator (voltage on battery was 12.5V or below when car running) - car eventually died while driving around
- I replace the alternator on 3/21 (see thread above), and the battery light goes off on first restart, (Mini) battery charging fine at 13-14V when car is running - I did NOT replace the belt, because it was not stretched, not glazing, not cracked - tension checks out fine
- 11 days later on 4/1, battery light comes on, power steering eventually goes off
- I replace battery with a new one from Costco - battery light still on after car starts - voltage across the battery is at 11.89 (and dropping) when car is running (and when car is off)


I gave up (as DIY project, since we need the car immediately) and brought it to a mechanic this morning. He thinks the remanufactured alternator is bad (after 11 days?). The alternator was the exact same model and part number (as inscribed on the alternator body) as the one I took out of my car. Ground cables that I can see visibly check out fine, and the alternator harness is in place, and battery terminals have no corrosion and are tight. I didn't check the whole electrical wiring between the battery and alternator, however...

Any thoughts? I'm also thinking the alternator died again, but perhaps something is causing a surge or strain on the alternator to make it die prematurely? At 40K I already thought it was too soon for an OEM alternator to die, now the second one goes out in 11 days and 200 mi.


Thanks in advance

 

my years of experience in the world of car audio I have seen this many times. it started with your battery. Most car parts stores couldn't test a battery properly to save their lives. Your battery had a cell that shorted to another, which in turn ruined your alternator. the replacement of your alternator with out replacing the battery wore on the new alternator. I would do the following: replace alternator under warranty as well as the battery at the same time, both should be cost free to do. I am virtually certain this will fix the problem. The only other spot to check is the starter, and its electrical connections. Good luck
Chris

 

Hi Chris,
Thanks for the reply and your thoughts. If it's as simple as a bad battery causing the alternator to die, that would be great news for me. I'd think though that shorted cells in a battery wouldn't charge up correctly, but I was able to charge up the original Mini battery to around 12.7V overnight.

Re: warranty, yes the alternator has a lifetime warranty as a part, unfortunately I replaced it myself. Since I'm in a rush to get this fixed, I'm going to have to pay the mechanic for the new alternator and labor, and then return the replaced alternator to Kragens for a refund (and hope they don't balk at the used part return, since I already returned my Mini OEM alternator for the core charge refund - fortunately I charged with my AMEX, so I'm protected if all else fails). The battery is new from Costco, and I just put it in last night, so hopefully the new alternator and the new battery will be the solution.

Yikes, out about $300 I didn't expect...

 

It's more likely that the alternator rebuild was shoddy as bought from Kragens. It is worth the money to buy a BMW/MINI factory rebuilt than a non-OEM. It may have the same part #, but it's rebuild location and quality are very different.

If you battery had a shorted cell it wouldn't hold a charge long after being taken off the charger and your alternator would be throwing everything it could to try and keep it charged.

By this time I imagine you've already spent the money to replace the alternator, but I believe a new alternator (again, preferably OEM) will solve your dilemma.

Don't expect that Costco battery to last too long either....

 

Thanks, all, for reading and for the responses. The car is running fine again. I'll just have to see if Bosch does better rebuilds than Autolite.

 

I am an engineer for a starter/alternator manufacturer (not Bosch), a bad battery will not cause an alternator failure. Batteries typically fail by load and vibration and a cell actually goes open circuit not short circuit. Any alternator from a reputable manufacturer (and I would not include in that remanufactured / rebuilt units from big box retailers), is tested to run at full load and max temperature for hundreds of hours.

A failure at 11 days is most likely simply a defective replacement part. But diagnosing via the web isn't the most accurate method either. . .