Air con malfunction

Hello , can anyone help ? I have a 1995 E38 730i that has behaved itself for many years until recently . The symptoms are that the heating/ventilation system seems to have developed a mind of its own, ie redirecting flow to vents continuously at a whim , the air con turning itself off moments after being turnt on and heating one moment then blowing cool the next . I suspect some kind of ecu or cotrol module is to blame but have no idea where it may be sited or if I will be sending myself on a fools' errand .Any thoughts or suggestions would be much appreciated .