This forum has been a great help in the past, hoping for a miracle here...

2005 Mini Cooper S R53, Chili Red
122k miles, not original owner

Car has been great the last 10k miles or so, hard a stall, limp mode, CEL light and others come on a few months back after getting a huge splash back from a truck. Car went into limp mode, pulled over, waited a while and then all was fine, except the huge amount of slush tore up the already damaged plastic skid plate underneath, so i took it off...

All has been great since, until last week when during a slight rain the car again went into limp mode, CEL lights on, battery light also, no overheating. I was able to get it home with a few stalls and restarting the car.
I checked the battery with the vehicle off, it was about 12+ volts, but was not getting any charge from the alternator when I started it up. It would run ok, then eventually the battery light comes on, then limp mode. Battery was getting drained, had battery checked and it tested good. Figured alternator was bad.

I pulled the alternator, got it checked, one place said it was good, went to another and they said it was bad. I got another alternator, installed it, checked for it charging to the battery and it was. Meter was showing 14+ at the battery when running!! I let it run a while and all seemed fine. Buttoned everything back up, went for a test drive, all was fine for about 10 minutes. Then I turned on the AC to test and about a minute later the problem came back, CEL, lights, and now starting to overheat.
Ugg... I again pulled the alternator, went and got it checked, it still tested as good. I also checked the large cable from the alt. to the battery, it shows it's getting full juice from the battery.
Next on my list to check is the grounding straps (any pics avail on where these are?) and check the alternator relay, fuses. Any other info or direction would be great, I'm about at a loss of what to do next. One note, was getting a rubber smell (slight to medium) when the last failure occurred. I have since got a new belt to install, but my last one looked fine, maybe it had stretched? All pulleys look fine and spin as they should. The crank pulley has a slight side to side movement on the serpentine part only, is this designed like this to aid alignment or could this be an issue? The center of the pulley looks fine and does not appear to have any wobble or weirdness to it. Alignment of belt looks good. Any thoughts or suggestions greatly appreciated. Thanks all for listening...

 

I think you hit it. 2 things. Corrosion on grounding. Look for a pack of brown wires under the hood. There could be corrosion.

Next replace that stock main engine pulley with a fluid dampened harmonic balancer. Pricey but it will solve a lot of headaches in the future.

 

Thanks man.
Is that pack of brown wires located above the passenger side front wheel roughly?

 

Yup. Same one as in this post.

 

Great, thank you, mine look worst than that so I'll start by cleaning them up. Best just to use a small wire brush or some such?

 

Hi,
It is really important to buy the right battery for your Mini. The correct battery has stable voltage, where others do not. BMW has always had issues with voltage swings and your Mini will throw codes, if the battery fluctuates voltages. Some batteries also over charge 14.6 Volts and and undercharge and this will also cause code throwing and limp mode.
Break down and buy a good battery, or you could be fighting codes for a long time.
Itsme Wayne