alternator/charging system problem
 

I replaced the alternator on my 2002 3.0 X5 with a new Bosch 140 amp alternator.
With the car on I get 13.7 volts, and when I turn everything you could think on I get 12.5 volts, is that normal?

The other problem is that when I accelerate very fast and the RPM hit 4k or more the battery light comes on for a ¼ of a second, but if I accelerate slow pass the 4k rpm mark it the battery light doesn’t come on.

Any suggestions?

possibly the belt driving the alternator is slipping under extreme power .
if you had it replaced very recently it may need time for the belt and pulley to settle .
just my guess from your description .

I'd think that if it does the same thing with the new alternator as it did the old one, check the connections at: back of the alternator, jump start connection positive post, engine ground. I have seen it before where the engine ground cable (at passengers side motor mount bracket) had a funky connection and caused a poor charging output and weak starter due to lack of ground path.

Thanks for the reply guys, it never did that with the old alternator, the old alternator stopped working completely so I replaced and now is doing that!

I will check the tension on the belts and the connection on the cables!

why did you post this in the lounge?

I figured it would get more exposure :dunno: