My 2005 CLK320 ignition key first worked except for the starter position for which there was no response. After checking that the battery was fully charged and the fuses were okay with no better result, the key then failed to turn at all in the switch and failed to activate the door locks. Could this be because of the battery in the key. When the lock or unlock button is pressed the little red light on the key lights, but there is no effect on the car at all. Help please.