newby - 95 C-280 Battery Light on

[Jay Jay 2]

Hey - I'm a newbie to Forums - but hopefully I can get some help.
I have a 95 C-280. The Battery Light came on along with ABS and Brakes - but then the lights went off. Like an Idiot I checked my Brake sensor - and it was good to go. Suspecting the Battery - I read 12.3v static and 13.3 at idle. A Dealer rep suggested loose wiring so I checked. All good but the Battery check again read 3v (left the trunk open overnight!) Enough - I changed the Battery. All OK for a few minutes - but I can faintly see the Battery Light remaining On.
Alterantor? Voltage Regulator? I'm capable - but don't have the manuals. Suggestions?

[GVB]

How many amps is it charging? You can be charging at 14 volts but half the amperage out put. Check the amps, go to a shop who knows how to put a load on the charging system. You probably have a bad voltage regulator, and or bad diode in the alternator.