we have a C230 compressor

Is there a check engine light when u turn the key? What happened when it stopped working? I need more detail? Were u driving when it stopped working? Is there any light on dash.....like a yellow lock flashing when u turn the key? Any noises or just silent??

Did you resynchronize the key after your battery was replaced??? Open your leather bound owners manual in the glove box and look under "Key synchronization" I believe this may be your problem. The owners manual gives you the steps to do this....easy. just read the book and relax....u will get it synchronized