Charging light

[landon]

My charging light has been glowing for a couple of weeks, mostly at idle but it seems to be more persistent at rpms up to 2000. Light goes at out above that. Measured voltage at the battery and have 12.5v at the lower rpms. I revved it up and saw an increase - up to around 13.5v but readings were intermittent. When this started to occur i would see 14.6v for anything above idle speed. All connections and grounds have been checked and cleaned. Auto parts store checked the alternator and said it checked out OK. They said they can't isolate particular conditions? Stock reman. alternator and regulator have 60,000 miles. Bad brushes in alternator? Any other checks to do?

Thanks,

[Napes]

Have you verified tha the belt tension is OK? Worn alternator bracket bushings can cause the belt to loosen up, resulting in slippage.

Bob Napier

[landon]

Yes, checked tension. I was definitely getting slippage at higher rpms. I have new urethane bushings in hand but want to make sure i put them in the right alternator. I tightened the belt and don't detect any slipping at the lower rpms.

[OriginalOwner]

also keep an eye on this thread .....

http://www.bmw2002faq.com/component/option,com_forum/Itemid,0/page,viewtopic/t,373310/

Cheers,

Carl

[Chris_B]

and read this, as imbedded in that thread:

http://www.bmw2002faq.com/images/stories/faqs/charging_system/02_charging.pdf

A glowing charge light can be caused by excessive resistance in that circuit, but most likely is due to a bad diode in the AC to DC conversion unit in the alternator (there are several in parallel, and if one drops out, the alt output will drop (but not completely...).

[BPM144]

Turned out to be my regulator. I was getting 16-18v at idle at the alt when I did the Volt. Reg. bypass with the jumper wire. I also showed about 8ohms resistance when I was testing the 3 pronged plug on the alt, which could explain why my light was only glowing.

[c.d.iesel]

[landon]

Thanks for the replies and the diagnostics C.D. and Chris B.

My issue turned out to be the alternator. Regulator checked out OK. I am getting 14.05 V at the alternator and 13.98 V at the battery at idle speed. The difference seems reasonable for 37 year old wiring and right in the middle of the desired 13.5 to 14.5 V.