PLEASE HELP - Heat-A/C {Problem

Hello Room
 
IHAQ - my 2000 S430, has developed a little issue - It seems to blow gentle heat in the car/cockpit - whatever speed you set the FAN at -.........The FAN works fine, you can hear it buzz to powefull speed but still the HEAT or STRENGTH or AIR does not change
 
So in a nutshell - FAN works fine, AC is fine The pipes develops ICE on it :->, however the cabin just does not warm up even set to HI
 
PLEASE give me some pointers
 
Thanks
 
Nik