I've been getting this message when I turn the AC (occasionally), when I don't turn on the AC it doesn't appear. Checked the the alternator voltage and its fine. Could it be
AC Alternator For Mercedes W203 CL203 S203 C180 C200 C230 2711540802 271154080260 271154080280 A2711540802 A271154080280| | - AliExpress
How to replace alternator on a Mercedes Benz E C CLK SLK S Class – MB Medic
02 MERCEDES C240 W203 Battery Alternator Charging Starter Cable for sale online | eBay
ALTERNATOR FITS MERCEDES BENZ W203 C,R171 SLK Class,W209 CLK Class,W211 E Class | eBay
How to replace alternator on a Mercedes Benz E C CLK SLK S Class – MB Medic
W203 Alternator Removing.pdf
12v Car Digital Battery Alternator Tester For Mercedes Benz W212 C180 E63 C300 E250 C E Glk Glc Gle Amg X204 W205 W203 W204 - Battery Measurement Units - AliExpress