Air-Force-1

My friend has a 2000 E CLASS KOMPRESSOR.

The key he uses all the time works fine.The spare key opens the doors ok but when he puts it in the ignition it won't turn !

Any ideas folks

Thanks

ohlord

and such work on the i/r and the r/f part of the key circuit transmits a signal to the reciever in the rear view mirror. The ignition switch works on the r/f only powered by the switch.So it could be that the key radio freq. portion of its circuit are deado
that's all I can think of.
ohlord
i/r infrared
r/f radio frequency

Richard / E320

Does the key battery have anything to do with starting the vehicle, or is it only for locking/unlocking the doors and setting the alarm?

ohlord

it is good enough to open the doors then that portion is working fine,the ignition switch provides battery power to the key to allow the key to turn in the ignition,It is a very puzzling set of steps that all have to be done before the car will allow the start feature.Still think that if one key works and the spare does not except for the doors,then the portion of the r/f key circuit that communicates with the ignition is faulty,New style keys are avail and are programed by the company that supplies them to work with his ignition.
For a more technical explanation of the system
http://w210.pietrzyk.net/electrical_rclatapse.htm

have him get a working spare,murphys law dictates the other good key will get lost,dropped or fail.
Search raymonds posts on the supplier of the new style key.