diagnosing a dead-battery

[ke6dcj]

My wife called and said the W124 1993 500E wouldn't start. She diagnosed it as a dead battery, and I agree.

After installing a fairly new OPTIMA fully-charged, and the engine running the voltage read on 13.8VDC on my Fluke meter.

The same alternator (150-amp, 14 VDC, 1999 S500) in my wagon reads 14.1VDC, AND when I installed on the 500E over a year ago, I also tested 14.1 VDC.

The "battery" light on the instrument cluster isn't lite when driving, AND the voltage regulator is barely 14-months old.

I'm guessing either a bad alternator or regulator.

Any ideas ?

BTW: the "snow chains" button doesn't work anymore . . .

All fuses have been checked everywhere and tested good continuity (all less than 2-years old).

Neil