Battery not charging on 2003 S55 AMG. I'm old and my spelling and grammar have left the building.
Special tools needed - Small C-clamp, 6 point T50 star (torx) bit

1. Pulled up hidden menu on dashboard. Voltage at 11.8 volts.
2. Had battery and alternator checked. Alternator not charging.
3. Removed ground lead from battery
3a.Removed front belly plate from bottom of car (10 bolts)
4. Removed five bolts on bottom of fan shroud that supported lines. (There
is a small star screw that is hard to see and it has to be removed)
5. On top driver side of radiator, broke off plastic retainer on two
line holder to easily get to fan electrical connector
6. Removed fan connector by pushing in on both sides of top of connector
7. Removed top transmission oil cool line on passenger side of radiator.
8. Pushed fan towards motor and inserted a stiff cardboard between fan
and radiator
9. Pulled fan up and out
10. Removed the two belts
11. Removed cover on double idle sprocket on passenger side
12. Removed idle sprocket
13. removed both bolts holding alternator
14. Removed nut on radiator fluid resevoir and with lines connected pulled up
moved it to front. Held it with ties.
15. Drained radiator
16. Removed heater hose blocking alternator
17. Removed plug going to alternator
18. Using long extension removed battery lead going to alternator. (Very
tight - used impact wrench to take nut off)
19. Angle alternator and took out through top

Note: The old voltage regulartor was okay. The old alternator was bad.
Have 87K miles on car. Better to spend extra few dollars and replace
both. Took me a day but was taking my time and had to go get star
bit to remove idle sprocket.

Note 2: Before reinstalling alternator, use a C-clamp to reseat the bushings on
the alternator bracket. Otherwise, it will be very difficult to fit alternator
into brackets.

Hopes this helps. Good luck!