I recently bought a 06 mini cooper s with a bad alternator, I changed out the altenator myself and it seemed to be working as I had to boost the car to move it then after I drove around for a bit it was starting good and my batterie light was off. But a few days later the light is on and its not charging. I used a multi meter to test the voltage while the car is running and it isnt charging even at high rpm. I also hooked up leads to the alternator itself while the car was running and I only got the batterie voltage back which leads me to belive the alternator is faulty but I want to be sure before I drop another 300 on a new alternator.

 

Looks like a bad alternator, sux having to change out for another unit, but didn't you have a warranty for the one you just put in?

 

You might check your ground straps before you replace the alternator. Also, have you had the battery checked?

 

Good point on the ground strap, but the alternator would still output to a bad battery.

 

I take your point (and I'm no electrician) but if the main grounds (front and back) are faulty and the alternator, which has both a positive and negative, is not grounded properly will it work as designed?

 

I agreed with you on that. What I said is if the battery is dead/bad, the alternator with still have an output.

 

I checked the batterie and it is good under load, i have checked one of the ground straps, but my thought is that if there was a bad ground that was only affecting the operation of the alternator i wouldnt be getting the batterie voltage when i hooked up directly too the alternator(not an electrician mechanic tho). I guess ill have to suck it up and take her apart again for that danm burried alternator.

 

Yeah, it looks like that will be your only recourse. I've put Scarlet in Front End Service Mode so many times, I got it down to around 20 mins. Use the bolt method so that you slide the radiator forward enough to get to the alternator. Since you have it on FESM, have you checked for leaks, (Dip Stick O-Ring, Crank Sensor O-ring)?
Hopefully you have a Warranty on the alternator...

 

At some of the parts stores like AutoZone they can bench test the alternator.