Battery disconnected and key wont go into lock

SOURCE: HELP HELP !!!!!!! Electric fault i think !!!!!!!!!!

1....ensure the battery in the "Key Fob" is OK............Press either Lock or Unlock button for more than 1 second, the lamp on the fob will light if OK. Change battery if it does not illuminate! 2.....if battery on fob OK.......Re Syncronise the key fob to the car by:.... a brief press on either button twice and within 30 seconds turn Key to position 2 on the ignition lock
Hope that fixes it...let me know?

SOURCE: Boot wont lock from the key fob or open from inside the car

Why not take mit back to the place that repaired it and ask them to fix it properly?
Ken S.

SOURCE: Mercedes-Benz 230clk coupe 1998 with dead battery

I had same problem with my 2002 CLK430. Dead battery with car locked. You can't open doors with the mechanical key (inside remote key), as windows need power to slide down slightly to allow clearance, so you can't access the hood release. The answer is to insert the mechanical key in the key hole for the trunk (boot). It will only go in one way, with the slightly larger grip part down. I found it easiest to turn with a pair of flat nosed pliers. Turn counterclockwise to the left to to the 11 o'clock position. Then push the release in and the trunk will open. Battery is located in the right rear quarter under the flooring panel that also covers spare tire. Hook up charger or jumper cables and power will come back on, as will alarm. To disable, just push the unlock button on the remote key. You should be good to go from here!

SOURCE: immobiliser on mercedes a class will not switch

The fob and car have to go to the dealer to have it reprogramed.

SOURCE: c240 mercedes key wont turn seems locked

I have a 2001 C240 with the same issue. I removed the positive battery cable from the battery and kept it off for 30 seconds then replaced it. Everything was reset and the key worked.