I was wondering if anybody knows how to replace the battery on a c230 key. It looks like it has a little door on the side but I dont want to break the key.

 

If you have the key with the alarm button that is round. take out the valet key and you will see when you look inside a small pin push that pin in gently and pull up the top and there are you batteries, make sure you follow polarity.

 

C280 wizard is spot on. Check this link for more info

http://www4.mercedes-benz.com/e/cars...nwechseln.html