Electrical problem
1999 Mercedes Benz E200 Automatic 123000 miles

i kept the car for a long time and the battery of the car was dead. than i changed the car battery . but still the same problem earlier when the car was fine i use the infrered key to the pannel where the key uses in the dash it will automatically turn on the power. now the problem is when i use the key to the dash nothing happens. but the central locking system is fine now when i changed the car battery and also the keyfob battery also working fine because from it we can lock and unlock the doors. what would be the main course for this and is there any backup battery in this car.