Mercedes-Benz CLK-Class Owner's Manual page 359

Practical advice
Changing the key batteries
Auxiliary heating* remote control
You need two 12V pin batteries.
1 Batteries
2 Battery cover
356
Slide off battery cover 2.
Remove old batteries 1.
Insert the new batteries. Observe the
plus and minus signs in the remote
control casing.
Slide the battery cover back onto the
remote control.
i
When inserting the batteries, make sure that
they are clean and lint-free.
Test the auxiliary heating functions on
the vehicle using the remote control.