I have a C240 w203 model with the old shape plastic three button key. The key intermittantly work to locl/unlock the car and when it fails I have to place it in the ignition and turn the car on and then the key will lock the car. I have tried replacing the batteries but the problem still persists. Does the key need re-programed or If I order a new key from the dealer would that work? I need to order a new key as when I bought it the car only came with one spare key. Thanks for your help.