Is my alternator on the way out?

[JazzMan]

My alternator seems to be behaving in an odd way. When you start the car its does not charge (on idle and a bit over). Only once you rev the engine over 2000RPM does it start charging. It then contunies to charge even on idle. Any ideas?

[jmc330i]

Ive got the same thing on my M20, although it doesnt do it all the time.
Battery light stays on until a quick blip of the throttle and then its all normal.

Do you have a problem with the alternator belt? I have to tighten mine once a week.

[stranter]

Same with me on my 318i M10, had it on a 518i E28 too, nothing to worry about, my battery has always charged perfectly!

Stewart

[JazzMan]

I've not been able to take the car for a drive yet this was just from testing on the drive way. Belt is brand new. I will check and make sure its tight enough At least I know I'm not alone with this odditiy

[jmc330i]

Brand new belt on mine as well, but it still needs tightening every week

I am still running the 2.5 off the 1.8 M40 battery and thought that might have something to do with it - over working the alternator or something???

Must get a proper battery for it

[browny]

When you talk about charging, how do you know if it is or isn't. My car may be doing the same thing. When I start it the battery and (!) lights stay on until the car is revved to about 3000rpm then both go out and stay out until the car is turned of and started again. Same things as you guys?? Whats the fix?

[JazzMan]

I have a voltage display, its sits round 11-12 when the alternator is not charging and 14ish when it is. There is also a battery warning light on the dash - when thats on it's not charging.