Sound just like what my w123 went thru last fall......The initial test of the battery was good; but 3 days later, the battery test failed. Sounds like a failing cell in your battery. Charge the battery up and then go to AutoZone and have them test your battery.

Of course, I replaced the alternator first......so maybe it was the alternator AND the battery. Or maybe the failed alternator caused my battery to die.

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daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
No longer selling Cluster Needles Paint
No longer selling New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more