The performance of automotive air conditioning systems could be improved by utilizing more effective control algorithms. This paper describes the development of a real time implementable optimal single zone temperature controller. A bilinear model of the process, including a disturbance is used. A one step ahead control is derived by parameterizing the control on a short horizon. The implementation of the algorithm is demonstrated with both a simulation and an experiment. The results indicate that the technique can produce substantial energy savings and improved rider/occupant comfort.