Mercedes-Benz 2008 C-Class Operator's Manual page 430

3 Batteries
4 Contact springs
Pull out batteries 3.
Using a line-free cloth, insert new bat-
teries 3 under contact springs 4 with
the positive terminal (+) side facing up.
Return battery compartment 2 into
housing until it locks into place.
Slide the mechanical key back into the
SmartKey.
Check the operation of the SmartKey
or SmartKey with KEYLESS-GO*.
Practical hints
Replacing SmartKey batteries
429