Hi from a new UK member. I have recently acquired my 1998 SLK 230. Central locking works fine using both the remote and the in-car c/l switch but the key will not lock or unlock the doors when used manually. The lock barrel turns freely (and soundlessly) through a quarter turn in either direction but that's about it. I'm worried that should either the battery or a component of the system fail, I'll find myself locked out! Only other possible clues(?): boot locks reliably with key, new MB 74 Ah battery fitted by an independent specialist a couple of weeks ago and the car has a Scorpion alarm, the mysteries of which I have yet to explore. The boot is completely dry. Any ideas would be most welcome.