stable/unstable conformations

 Hi Netters!
 For my investigations, I calculate the energy of molecules containing the
 ethane-rotor. To calculate the energy difference between the 3 canonical
 rotamers I start with 3 different structures and optimize them.
 Unfortunately they all give the same result (only one rotamer). Any suggestions
 how I can solve this problem. I will send the result of my question in this
 Thanks a lot
 Kay Kreidler