Abstract: A control system for controlling the operation of a heating or air conditioning system, especially for the passenger compartment of motor vehicles. The temperature in the compartment is maintained by an electronic controller which receives temperature-related signals from one or more temperature sensors. The electronic controller is connected to an air pump which may be operated as a source of pressure or vacuum and is coupled to a pneumatic actuator which moves a final control element, for example an air flow valve or a cooling water valve. The air pump supplies a continuous and reliable source of pressure or vacuum independently of the engine manifold vacuum. The air control conduit is coupled to a ventilating line which communicates with the atmosphere through a fixed or variable throttle.