Strange issue around battery light coming on
 

Within 1 week both my 300TD and 300SD developed the same symptoms - almost.

When the cars are started without throttle, the battery light is brightly lit.

The battery light on the 300TD goes completley out if.
A. I rev it anything more than 1500 RPM and then the light remains out no matter the RPM.
Or
B. I release the emergency brake while it is at idle, the light goes out 100%.

On the SD, the light does not go out 100%, but is very dim, however A and B above take it from bright to very dim. Also the more electrical load the dimmer it gets (headlights on, battery light dimmer than with headlights off)

I had thought the alternator, until the emergency brake being released impacted it. Both regulators have plenty of brush left, check about 1 month apart, each within the last 10000 miles.

Any ideas?

Thanks
Don

some ideas:
300td- A. the battery is losing some charge, when you rev it up the alternator or generator (what is it on these thing any way, I've had my head up the ass of VW's for the last couple of years) it charges quickly and remains charged ther after that, so it does not indicate low voltage from the altenator.
B. i cant remember if the battery light is next to the e brake light but if it is the Ebrake light could be lighting up the batery indicator as well( the oil light does that to my battery light on my Vw bus)
on the sd i would say a bad connection for the sensor, and the light is giving a false reading. and when you pull more power the ligh gets dimer just because your pulling more power.
just some ideas hope they help you find the problem
will

I had a problem with my 1993 300 SD, where the battery light
stayed on when started. Rev it up to approx 1700 RPM's and it would go out and stay out at any RPM's. The problem was in the
instrument cluster, which I sent away for rebuild.