Hey there, everyone. I've searched around and couldn't find much of an answer, so I'm hoping someone has seen this before. Basically, whenever I run the A/C, I can feel a pretty huge drag from the compressor, and it seems like the alternator has a tough time keeping up. Voltage at idle drops below 12V (from around 13.1-13.3V at idle with A/C off). The blower motor slows down significantly as well. In addition to that, on acceleration, I can hear a whine/howl from the engine bay that increases in pitch with RPM. I don't know if this is the compressor itself, or the alternator struggling with the added drag from the compressor, but the noise stops when I turn off the A/C. Also, the A/C is cold (around ~40F at vent). On top of that, the headlights dim when I turn the wheel at a standstill, even when the A/C compressor is not running. PS pump shouldn't be an issue there, though- it was replaced along with its cooling fan around 20k mi ago under the extended warranty for that part.

However, here's why I think it's the alternator: I put in a fresh battery and all these problems stopped. The odd noise goes away, blower motor stayed at a constant speed, headlights stopped dimming. Literally the next day, all those problems came back. So I can assume it's not charging adequately.

I stopped by a Mini dealership to pick up an oil filter recently and asked the service advisor about this. He offered to take it for a drive with me- quite a nice guy. He didn't hear or feel anything abnormal though, except that I needed some new LCA bushings (I've since replaced those). Additionally, I've seen some posts saying "yeah low voltage at idle is normal, it's not a strong alternator," etc. I just really don't think these issues are "normal," especially when they weren't present with a fresh battery. What do you guys think?

 

Being in Raleigh have you checked out G3? Chris the owner works on both MINIs and BMWs. I have several friends that have G3 maintain/mod their cars.

If you are able to turn your own wrenches; as you say the lights dim when you turn the wheels and as the power steering pump is wired directly to the alternator via a 100 amp fuse in the bottom of the engine fuse block, would be logical to think alternator, but then if you have bog downs when the AC is turned on, the compressor may also be going as I don't know why low voltage provides resistance to the compressor.

 

Actually, I have! I stopped by right after he opened the shop since I lived off Glenwood, maybe 3 minutes away. I'd bring it by there... but unfortunately I live in Texas now! Forgot to update my profile.

But yeah it could easily be both. I think I'll start with the alternator and go from there. I didn't want to spend the time/money replacing it if it's not the problem, but I guess a new alternator would be a good idea anyway considering it's 13 years old by now. Thanks!

 

Would think if you remove the belt the alternator pulley should spin without too much effort.