My 2005 C320 Remote key is not working properly, i have to take the key very close to the driver's door opener, before it can unlock and lock the doors. what could that be and what to do?

Uses a common size battery - you do not need to go to a MB dealer.

But until you do get the key fob battery changed, if you really need the extra couple of feet try this... Hold the key to your temple (the one on the side of your head, not the one with budist monks down the road) and press the button. I saw this tip on uk top gear a while ago and naturally gave it a shot. Yes you will look mental to onlookers, but you won't care because YOU CAN UNLOCK YOUR CAR FROM 3 FEET FURTHER BACK THAN YOU COULD YESTERDAY!!!!!

Ask Mercedes to admit that there is a 'latent' problem with the key identification system,and for them to do something about it - at their expense??? This answer applies to ALL Mercedes owners with this or similar Key -No start problems!!!!!