How to Install Batteries in the Mercedes Key

1. Turn the SmartKey over so the buttons are facing down. Press down on the plastic back-up key tab to unlock the mechanical key. Keep the mechanical key in its pop-up location, then slide the mechanical key across the SmartKey. Sliding the key will unlock the battery compartment. When the batteries do not work on your SmartKey, use the mechanical key to unlock the doors and start your car, until you get a chance to change the batteries.
2. Pull the plastic tab on the back of the SmartKey to remove the battery compartment.
3. Remove both batteries from the battery compartment. You should replace both batteries at the same time.
4. Put the two new batteries in a lint-free cloth, then insert them underneath the contact springs with the plus (+) side facing up. The batteries should be clean and lint free before you install them.
5. Slide the battery compartment back into the SmartKey. Slide the mechanical key back into the SmartKey.
6. Test the SmartKey by pressing the remote buttons and start the car to make sure it works.